It's not fun to knit for myself. I have average body issues; everyone wants to be taller, thinner, have a better (fill in the blank). Every stitch is a reminder that (despite what my mother told me) I am NOT perfect.
The Turks hang small mirrors from chains on their walls; the mirror backs are ornately decorated, because they are flipped over after use. To them, like the Quakers, it is sinful and vain to spend a good deal of time looking in a mirror. I struggle with issues of vanity when I knit for myself.
On top of that, it's tough to produce thousands of stitches imagining how cute a garment will be, and then find it doesn't fit, the neck doesn't lay flat, the pattern is crap, or, as Heather put it in Romy and Michelle's High School Reunion, "This dress exacerbates the genetic betrayal that is my legacy. " Every garment IS a crapshoot, and the one I linked to is a good example. Knitters gamble.
Mostly, though, I think knitting for myself is lonely. My friend Shui Kuen once said "When I knit for my mother, I think of my mother." I have no happy thoughts of surprising friends and family with a new garment, a hat, a pair of socks.
I know-I got issues.