This is not necessarily the case. Indeed, you don't need to use Blue Wallet INSTEAD of Alby. I use Blue Wallet WITH Alby so I can easily use my Alby wallet as a daily driver lightning wallet outside of Nostr and without having to use the browser extension for everything else.

Blue Wallet allows you to import many other lightning wallets, too, so it is a good tool to have, even if you aren't planning on hodling long term.