Well core was the first wallet and will always be there, it's up to people to find ways to monetise their efforts, some will do it open source and work with donations, others will couple their wallet with other premium services or as part of a tech stack

IE blockstream does a whole lot of things and offers a wallet almost like Microsoft offers an email client as part of its office stack

You'll get wallets with LSPs and running routing nodes that earn fees that way, although I doubt it offers much of a revenue driver right now

Before the crackdown Wasabi and Samaouri had a healthy revenue through coinjoin coordinating

Some companies might also fund or buy equity in these businesses and run it as loss leader because it helps onboard users