For a reason that makes each and every human on a planet do whatever they do: because it’s fun?
Are we talking about the same thing? I mean yeah, these staffs are similar, in a way that a sword is similar to a hammer - they both have light attacks and heavy attacks, both can be used to block and push.
These are completely different weapons on the other hand, and not just because beam staff has 3 fire modes, while bolt staff has only 2. Bolt staff is much better at dealing with groups at range and in tight spaces, while beam staff is much better at dealing with elites and enemies up-close.
Does bolt staff need buffing? Absolutely, it’s charged attack needs some love. Is it a bad weapon? No, not even once. It’s probably the second best staff the wizard has, because Fireball and Conflagration staff light attacks are so weak, though the latter part is arguable, since their charged attacks are so very strong.
So if you don’t like a weapon and don’t wanna use it - it’s completely up to you. But coming here and telling something is bad, because you do not understand it - that’s weird.