For me, the best way to describe it is that I strive to feel in control in progressively more difficult environments. That's the mental state I'm looking for. The progression of the mental state goals are easy to follow:
Top Rope (rope already set up above you): "I feel in control despite me being 40' off the ground"
Lead climbing (bring the rope up and clip into the wall as you go): "I feel in control despite me having to take a big fall if I fail"
Outdoor climbing: "I feel control despite me climbing real cliffs outside"
And you can follow this all the way to free soloing, where you can feel in control despite having no safety net at all. I'm not going to pretend that I understand Honnold, and I don't free solo, but this line of thinking makes sense to me.
The other off topic reasons I climb are:
1. Getting better at a sport, just like any other sport/hobby.
2. I like the outdoors and adventure, climbing is a great way to see things from a perspective most can't.
3. Fitness