Just to add to what everyone else is saying, they could simply believe that showing these demos is what attracts the smaller devs. People who are just getting

Just to add to what everyone else is saying, they could simply believe that showing these demos is what attracts the smaller devs. People who are just getting started will see this and see that Unity must surely be capable of everything they need, and it may even be trivial there, if it can also handle this. It's also a piece of aspirational marketing. It doesn't make sense to show the reality of the mobile game space as that won't get anyone excited. It's what you could do, not what you will do.