Per Jasper Janssen:
But that's more vandalism
than actual *theft* (although you can't tell the difference as a victim,
of course).

I assumed that it was people stealing bikes just to ride them home.

That's how it was with cars when I lived in Hawaii - at the end of a school day,
kids could steal your car, drive it home, and just abandon it there. The ones
who did this tended to come from a specific section of town and the cops would
just advise people to look there for their cars.
--
PeteCresswell