That's how it is with me. With straight silky hair, it's just a matter of time how long it gets when I don't bother to get it cut. It's the default. (Not that this has anything to say about the health of that hair...)
A long time ago I had one of those bad trims that ended taking off 5" more than I asked, and didn't get my hair cut for about 5 years, just wearing it in a braid all the time. Next thing I knew, boom, I couldn't reach the end of it with a brush.
Other people (read short-hairs) think that growing hair long is a conscious decision in the same way that deciding to cut or perm can be, rather than either an ongoing process or even simply a failure to act.
I was once in a meeting with a woman I had not seen in a while. Her hair has always been chin-length, limp mousy blond. She mentioned to me that my hair had gotten long. I said, "It does that." She said, "Mine doesn't."
My daughter finally looked at me a year ago and was kind of shocked at how long my hair had gotten. "Mom, you're hair's too long!"
sez you...