Hmm..I would have to say:

1.) it keeps me going

2.) it feels like "home".

There is almost always enough going on around here to keep both playing and the interest in the instrument high.  It is a rare day here that doesn't have someone putting up a recording or video or mentioning a piece they are working on, and that just sort of naturally leads to thinking "I have to try that" and picking up the instrument and playing a while.  Or someone will say something interesting about violins/fiddles that will set me off on a websearch where I will learn some interesting and useful things.

Even from the first rather dreadful sounding bit I ever recorded and put up on the forum, I got advice and encouragement, as most people here who put things up do.  That is sort of rare.  Not just on the Internet, but even just among groups of musicians, the degree of shared support and encouragement one sees here are a rare commodity in the world. 

It is just a very good place that FM has going here.  And I have been in enough "not so good" places to recognize that.  If you haven't ever run into groups of fellow musicians that tend to be unpleasant and are far worse examples, then I sincerely hope that the world will be kind enough that you never do.  But I can tell you, this place is special and unusually good.