I've always seen it as a way to key people in to the fact that this is something one did just to try it out, and not something one is emotionally invested in. Communicating that may, in theory, get people to be more honest/brutal in their opinions rather than trying to "be nice" about it.

It doesn't necessarily mean "look, I did it in a weekend!" but "hey, I was messing around with this in my spare time..."