The Kamehameha

It is popular because Goku is one of the most iconic characters in fiction and it's his signature attack. So, yeah, it's going to be popular. Everything about it -- from the pose to the attack itself -- just looks cool.

I think that Goku should always use it. Let's face it: in the real world, if you need to use a Ki attack and you had a signature move, that would be your go-to. There's no "overusing" an attack because a big part of the series is Ki blasts. Why would Goku suddenly change it up to a different attack? It's not like he's using it to blow out candles, lift Chichi's skirt, or revive people from the dead. As long as it keeps its intended purpose, I don't see a problem with how often it's used.