I've been towering a lot recently and I've yet to fully understand this term or why people treat it as if it is a problem or bad thing. If people want to tower, get to the reward threshold, and then stop, why is that a problem? They should continue for 4000 more hours for the same reward? That just seems illogical.
If you want to actually make the term something insulting and sensible, call the people who tag along at the very ends of guilds hat chasers, or call the people who join these guilds and just AFK a lot and spam guild chat so that they get attention for their "activity" hat chasers.
Anyway, I'm sure the term just comes out of spite, immaturity, and jealousy. If people want to tower with their friends and get a reward out of it, I don't see why they should be harassed over it.