Graffiti artists

You've got it spot on

Graff writers generally aren't fans of street artist.
Graffiti is generally done illegally and is self taught or passed on from toehr writers
In my view they generally look at street artists as people who only paint legal walls, don't follow 'the rules' of Graff, do it for the wrong reasons. I could go on here
Then there's the whole stencils/projectors etc. That Graff writers can't stand due to it being seen as colouring in

Tldr: street art is usually pretty pictures and Graff is hard to decipher and usually done by writers for writers not general consumption