I believe almost all of the people watching anime or reading manga get them from various sites like watchop.com, Crunchyroll, anime44, etc., and similarly for manga there are various sites. But are these episodes/chapters really free of cost for the audience? I know that these companies have their major source of income from merchandise and all other stuff but the episodes/chapters are available on net so easily that too for free. Aren't there any copyright violations? If there are why don't these anime/manga companies do something about it?
Yes, there are some legitimate websites on which you can read manga and watch anime for free. Crunchyroll is one of them. While Crunchyroll started out as a site that streamed anime without licenses (i.e. illegally), they are now fully legitimate and above-board.
Of course, Crunchyroll has to pay for licenses for the anime they stream - the producers over in Japan aren't just going to give it away for free. So how does Crunchyroll make money? I don't claim to know Crunchyroll's business model, but (as this article points out), they have venture funding, and they sell premium memberships, as well as anime-related merchandise. They also show ads to non-members. Lots of websites follow a business model in which users get lots of functionality for free - for example, this one!
The other sites you mention - "watchop.com" and "anime44.com" do not appear to be licensed purveyors of anime, so in their case, yes - they are probably infringing on the copyright of the owners over in Japan. They presumably aren't paying the licensors in Japan a dime, so it's not surprising that they can (illegally) show anime for free. You probably shouldn't use those sites.
Allow me to quote from Logan's answer over here (emphasis added):
Also, if I'm remembering correctly (and please, do correct me if I'm wrong; I'll try to dig up sources for this later), anime licensing deals are typically a flat fee - the licensees outside Japan pay the licensors in Japan a fixed amount in exchange for the right to stream the anime, or sell physical copies, or whatever.
What this means is that the licensors don't care how many times the anime is streamed or sold or whatever - they've already got their share, and if piracy reduces the number of people outside Japan that watch the anime on Crunchyroll or whatever, oh well! It's not their problem at that point.
Sometimes anime streaming is free, but mostly it is usually geographically monitored. E.g. Hulu uses geographical blocking to stop people from other countries and regions outside of the USA from streaming content.
The reason they have this is due to probably copyright issues. Sites like anime44 are usually considered illegal sites, but because copyright varies of many factors including location it is usually hard to shut down sites like anime44.
As said in the comments they are usually free because sites such as Crunchyrolls often get income from Premium Membership Users and products/merchandise that they sell on there site including Koruko No Basket figurines and much, much more. It is also most likely that they earn money from clicks on ads, or on how many people view ads in between the animes that you see for free. It is also likely that they might have sponsors too.
Edit: One thing that these site infringe on is:
Unfortunatley there are some complications to this since if you are in a country where Copyright laws arent the same or enforced then people can get away with this, and if they are streaming it online to everyone one around the world, then it isn't exactly for personal use then is it?