If someone tries to attack me at the top of a hill that I’ve just climbed, not only do I have to get off the bike (clumsy, if you’ve ever seen me try to get on or off a bike), but I also will also sprint at decreased capacity because I’ve just been working oppositional muscles, and the ridiculous helmet will be bobbing in my face. I am not a triathlete.
Basically, I don’t think I like it when my transport time is a time of increased alarm. It’s supposed to be a break.
(also how do I know if there will be a place to lock it? In Redmond I could just lock it against any sapling as a formality.)