I think you're trying to shift your obligation from showing why you worry about blowing out a knee, breaking your foot, or getting sucked into the prop when stepping off a slowly-moving boat, to showing that you are a badass in other areas of your life, which seems totally irrelevant to me.
Maybe you are not only risk-averse, but also inconsistent?
How did this become so personal?
I'm adverse to dumb risk with no reward. When I ride a bike, I wear a helmet and body armor. Sure, I 'could' ride without, and some folks will even call you names for wearing a helmet. OTOH, I'm aware that people have died in 0 mph spills in a parking lot, so why risk it?
Stepping off a boat with it in gear, gets you little to no return. I don't fear breaking a foot, but I am aware that it happens. Have you NEVER tripped? Never mis-judged traction or distance?
and it does not take all that much to REALLY mess something up inadvertently. I've been around boats enough to know quite a few people with freakishly torn ligaments, broken bones, etc. it happens! you can stay at the helm and lasso a cleat. you can come to a full stop and then step off. you can come to a full stop and then give it a little reverse motion if ya want. or I mean, MY GOD!!! you might even have to do it a second time!!
And I have in actual fact stepped off a boat onto a dock and ended up on my ass. Having an unattended boat in gear at that point serves what purpose?