It makes sense why Luffy keeps Bumsopp around when you realize Bumsopp is the crew clown

Bumsopp is a low tier sniper, he can hit from far away once in a while but we have seen his projectiles don't matter against top tiers. Compare him to Van Augur, who fodderized Cracker's biscuit soldiers. We have even seen Usopp struggle against fodder in Wano and a stupid cat in Elbaf.

So, why keep him around, when Usopp fails to keep up with the crew and rarely pulls his weight? We know Luffy hates weakness and especially cowardliness, he has said it many times and even criticized Momonosuke early on for it.

Answer: Usopp's main role is to be the crew's clown. He exists to goof around and entertain the future pirate king, like a court jester. He isn't meant to be a brave warrior of the sea, he is meant to be a fool and serve as slapstick comedy for everyone else.

This is why Luffy tolerates Usopp's presence in the ship, despite Usopp failing to meet expectations. His only role is to entertain, and maybe snipe once in a long while.