Well...he originally was just going to side with the stormcloaks, but as I started my journey and met with the Companions, I thought he could bring some brain to the group. Also, he's good at smashing things. There's that too. Hircine's also part of his background (which I won't get into because it's complicated character history stuff that doesn't really matter), so I decided the actual reason he went to SKyrim was to wander around and find a werewolf group (the Companions).
As far as followers go, I only use them when I remember I can~ Like when I first got Lydia I used her until I "accidentally" killed her in a raid on an Imperial camp. Then I went without for like ten levels and the cycle continued with another follower and yadda yadda yadda
He also joined the College of Winterhold because he wanted to learn more about Alteration and Enchanting since he originally taught himself how to do them; this was fairly late in his journey, not too long ago.