I sort of already partly answered this in the other forum you mentioned. I take pics because I enjoy it as a combination of two of my hobbies, Joes and photography. And I love the challenge of attempting to capture that "perfect" shot - I haven't done it yet, but I'm having fun trying!
But more than that, I love the process of turning an idea into reality, seeing if I can create in the "real world" what I can picture in my mind. Sometimes something will inspire me in a flash of brilliant light, other times an idea will germinate and grow over weeks, until it becomes something worthy of a photo. Other times I'll wake up in the middle of the night with an idea, and plenty of times I'm "dry", without a clue as to what to shoot next. All in all, it's the mental stimulation and creativity that really have me hooked.
