At my company, one of the complaints some Asana users have is they can’t find projects they are part of. I know, it should be pretty easy for them to figure out. There is search, links in emails, links in tasks, etc. But still, some find this challenging.
For myself personally, I almost always favorite any project that I am part of, because it makes it easy to get to that project from the sidebar. However, I think many people do not do this, and having the projects in their sidebar automatically would alleviate some of the confusion. So I think it would be helpful to have a preference to “Automatically favorite any projects I am added to”. People could easily un-favorite them of course.