Its seems that folks who aren't sure what to make of bicycles choose simply to make off with them.
No one would mess with someone else's car the way they do bikes. But it's not just because bicycles are less expensive than cars (ignoring that many bicycles are more expensive than many cars), because most wouldn't even mess with someone's lawn chair or garden hose the way they do with bikes.
Bicycles are seen as toys, as non-owned non-property that can be made use of without permission or care. "It's just a bike" is our national slogan of self-justification. A bicycle is less than a thing, it's an inconvenience, a joke, a badge of failure.
Except that a bicycle is none of these things. In the very least, it belongs to someone; it matters to them. At most, it is a vehicle that will take us to a better future. Regardless of where on this spectrum one sees the bicycle, I think it's more than fair to ask them to keep their hands off.