This is the answer: to learn stuff.
Just being connected to others with the same passions, and watching their stream, teaches me a lot.
Of course there is much random chit-chat of people you don’t know in real life, but you can easily filter that out.
Sometimes it is also fun being there, like yesterday, when a virtual snowball fight broke out.
So, should you join Twitter?
If you want to learn, yes.
If you want to have fun, yes.
If you don’t see the point, yes. At least try it out before you judge.