I do this when I occasionally stop at a walk-up restaurant. I'm only a few feet away, but it is a high pedestrian traffic area, if someone saw me dismount or made me as the bike owner and waited until I was distracted ordering/paying/getting my food they could make off with it otherwise. The helmet strap clipping the front wheel to the frame is just enough to slow them down so I'd catch them if they tried.

I've only done a few short tours. The last two, I brought a medium sized u-lock with me. Next chance I get to tour (likely next summer sadly), I'm tempted to spray paint a Palmy black. I also plan on mounting a ring lock.