Because Zaps are branded as bitcoin lightning payments with NIP-57 and therefore it will be confusing when people start talking about shitcoin specific zaps.
But hey, nostr is a permissionless protocol. Go build the world you want to live in.
Discussion
I agree different terms are necessary.
if only because monero zaps could observe 1st principles and be noncustodial
this new generation of nostr users are growing up thinking custodial solutions are normal