why don't more Brave users use the build in crypto wallet?

Co-founder, Scout Game. 
https://scoutgame.xyz

don't trust a browser software company to build a wallet + tend to switch across browsers

I do. If and when I have enough to sweat over, I'll move to something even more secure. But it is in Brave's utmost interest to make something secure, useful, and open source.

Eh, I just don't use web wallets much outside of FC.

Also Rainbow is better 🌈

Haven’t tried in a while but I remember not liking it when I did

Why should we use it? What advantage does it have over metamask, for example?