There are tons of different beam attacks like the Masenko or Galick Gun, why does everyone seem to go for the Kamehameha instead? Going as far as to have Cell use it as his ultimate move instead of the Final Flash he witnessed not so long ago, is it the best ki blast beam? Why? Buu also copied it as soon as he saw it, he didn't seem to bother with the other beam attacks
Well, the answer to the same would be very opinionated and not factual. Some of these may be interesting reasons why the same is popularly used.
- Toriyama wasn't sure as to what to name his Kame attack and it was his wife who came up with the same and it was named after the Hawaiian King.
- Also, the same attack is very iconic and it was introduced even early in the Original Dragon Ball Series by Master Roshi which was immediately mastered by Goku in a few seconds. Unlike the other mentioned attacks.
- Also, this attack has always been considered as a signature move of the main character Goku.
- The Dragon Ball Franchise is indeed very popular and even those who haven't watched the franchise have an idea as to who Goku is. Hence it makes a lot more sense for people to remember the signature move of the main character.
- Another fun fact is that Akira Toriyama did a lot of different poses until he finally decided on something which he considered cool and I think the hand movement made while launching this attack is also very iconic and popular and emulated by a lot of Dragon Ball fans. Hence this attack is easy to identify by simply looking at the hand movement which is probably why it is used a lot.
Source: Dragonball Wikia - Kamehameha