I work in a repair shop and we will do head gaskets, a lot of others won’t though because liability, in some rare cases the repair fails, we have had a few fail, and it turns out the issue is a hidden crack or something, of course then the customer is angry and it all goes sour because we don’t have xray vision and sending out for crack and pressure testing is expensive.

This is why they don’t want to get involved, selling an engine with a warranty protects them.