It seems that many renowned manga artists still prefer using traditional "hand drawn" methods rather than using technology to draw. Even people who use technology to finalise their art rely on pen and paper to sketch their initial outlines. What are the limitations of drawing using digital methods?
There are two primary limitations to an artist switching from traditional to digital media:
That's really all there is to it.
The two reasons go very much hand in hand; most artists will start with traditional media because quality digital media is expensive. There's no getting around it. A basic setup requires a computer with good graphics support, a software package that can be used for comics/manga production, and a graphics tablet (typically a higher end one like Wacom's Cintiq).
On the other hand, anyone can pick up some free scratch paper and a pencil or pen and start sketching. There's virtually no barrier to entry for learning traditional media. Once you start to get more serious about it, yes, traditional media can also get expensive (comic/manga art boards, multiple pens and brushes, various types of inks, screentones, alcohol markers for color pages, and so on), but you don't have to spend a dime to start.
There's a process of adjustment that takes time when switching from traditional media to working digitally. The two feel different, even if you're working with something like a Cintiq where you don't have to disassociate your hand position from what you're seeing. You're learning a new medium, and it always takes time to adjust to it. An active manga artist is working on a strict publication schedule, and isn't necessarily going to have time to go through that adjustment period; artists who are extremely popular will have greater demands on them, and those who are just starting out will have no ability to ask for schedule changes or additional assistants to work through the transition.
There are artists who do use digital media (Hiroya Oku, Asano Inio, Natsume Ono), and certainly there are some who would be interested in making the transition, but for many, it may well be simply a preference that keeps them from making the shift. They prefer the feel of a pen or brush on paper to a stylus on screen, and therefore have no motivation to sink either the time or cost into transitioning to digital. Working digitally has an additional limitation when it comes to assistants: either you are now a one-person show, or you have to sink money into a workstation with tablet for each assistant on your team. Particularly with popular artists who depend on their assistants to meet deadlines, there may be no choice but to stick with paper that can be passed around between the people working on the title.
There are no technical limitations. Multiple companies make Cintiq-like graphics tablets at various price points and functionality, allowing for a more "traditional" workflow for the artist. Multiple companies publish software that can be used to create manga pages, including screen tones and tools that emulate traditional media very effectively; any of these programs can export into any number of standard formats that can be read by the publishing company, which is undoubtedly using digital versions of all pages, regardless of how they're produced, to assemble their magazines. The only limitations are in the cost of transitioning, both fiscally in actual money spent, and the investment of time needed to adjust to the new media.
Sources: Manga Answerman - What Tools Does A Mangaka Use To Make Manga?, personal experience with various hardware and software
It is expensive and a new technology that would even cost the printing companies money. They would need new hardware and/or software to get the files in those formats, much more space on their machines (files in any graphic format are very large). It is actually so much more money for good digital animation art, especially when Manga artists each have a style. They have used "pens" for drawing and inking since they start drawing. Kubo, the creator of Bleach, always drew in school; he still will say he draws to draw cool stuff. So, I imagine most drew in class or at home with standard writing tools, and maybe a set of inking pens and color if they were into it.
As far as the monitors for drawing, yes they are cool, but artists often don't have one for the same reason I don't, they are expensive. They could probably get money through crowd funding faster than I could, but they would need something very expensive, not to mention the drawing programs. Anime studios don't use them (usually on weekly airing shows especially); the first draft and sketch is generally done on paper, the same way it has been for probably almost if not 20+ years. Drawing it, scanning and then adding color. I can imagine that actually take more time as well. Most well known artist/writers have an aid and maybe a few others helping them with the inking. Transition to all digital would be so foreign, I doubt we will see it happen, at least until graphic tablets, monitors ect. are easily available and the price is lower than now. A good one could be $1K, maybe $600, but they can be 3 times and even more. So if they want it to feel right, look right and be efficient it's probably going to be a lot of testing of different monitors, programs, brush add-ons, and more. It's not really feasible right now. I guess if one happens to have started using them a while ago and feels comfortable and can work more efficiently with the style remaining the same or better, they are not going to use it unless their work is better. They can't afford to show Toei an idea that was done differently than the usual methods so their style, and maybe even flow of work would not be the same.
Not to mention coloring would look way different. Would shading style change at that point? In manga many kinds of shading and small details are used. Think the parallel lines very close together and straight, that form of shading is unique to the art. With a graphic program you would need to place every line pixel perfect; they could use snapping or magnets, but that would throw off the next line to draw if it's a persons face or something. On a monitor instead of drawing those lines they could just pick a lighter color, or shade, grays would be everywhere. Maybe more color, but it wouldn't look the same; maybe close with the right brush, but not exact.
Expenses, tradition, experience, style, comfort level, and efficient work all play a role.