I frequently watch code because it is one of a set of projects. I don't care about that project specifically, but I like to see it is active, make sure they aren't going in a direction that will mean trouble could be headed downstream to what I actually care about and so on.

I also watch projects that I think could amount to a big deal, but are currently in the concept phase. That way as they get going and start solving a problem I know how it goes.

Finally I watch projects that are solving problems I may have insight into -- so I see places I can contribute.

In all these cases I don't fork because I am not engaged enough to maintain an active fork, since they you must manually pull the upstream master regularly... annoying if I'm not doing it because I'm involved. Then I can just clone from the head easily when it is time to fork or modify the code.