I bought a set of Wahl clippers in 1992 to clip off all me hairs or so just before I bicycled cross-country. And I've been cutting my hair and a lot of other people's hairs since then. Last time I did a hair-cutting place was probably 1992 or 1991 or thereabouts.
I like cutting my hair. It's kind of a nice way to sit down every few months and re-evaluate what I look like and play with my hair in the context of my head and face. Like sculpture a bit.
That's the artistic/intellectual answer. The lazy-ass procrastinator's answer is I do it because I'm too fucking lazy to drive 5 or 6 miles and then explain in English using monosyllabic words the hair-cutting person can understand what I think they should do.
The psychotic answer is that I'm practicing to some day grow up and be Sweeney Todd. But don't tell anyone....