...is everything else secondary?

He got a haircut because he was tired of it, it was getting in the way, bothering his eyes, and it was hot.

The fact that he was tired of it also played a role, but I disagree with the last two points:
1) It protects the eyes from the sun.
2) It keeps the head warm in winter

And if necessary, you can tie it in a ponytail, then the view is normal, and the head is not hot.