I’ve been lean most of my life with the exception of about 5 years when I gained 40lbs. My inspiration for getting to a low enough bf was simply the challenge of it. I will say I’m surprised how different 13% is compared to 16%. I’m motivated to get to around 11%. I really want visible abs this summer. After the summer, I’ll reevaluate.
I was hanging around 16-18% (not tracking anything) for about 3 years. When I finally dropped down to 11%, the difference was night and day. I went from feeling like just another guy to 'the ripped guy' at the beach, and my confidence skyrocketed. My wife started making frequent comments about how jacked I looked.
Some people don't care about stuff like that. It may be a shallow goal, but I like it. It's a good feeling. And on some level, I think it's why most of us work out.