I've seen the same things all over NYC. You can tell which bikes are abandoned with a quick glance:
- Chained & rusted solid
- Stripped of every last component yet still chained
- Rusted through and through to the point where you know it won't even roll none the less ride...
There are a lot of transient people in NYC. Some of the bikes aren't even worth the shipping to wherever the owner of the bike is going so they just leave it locked. Numb-skulls... Why not just give the bike away or sell it for a few dollars?
Bike parking in NYC is already scarce. Having abandoned bikes squatting on a packed rack isn't cool. Contact the owner of the bike rack or police & let them handle it. Or you could put a note on those abandoned bikes saying "Steal me! PLEASE? And put me out of my misery!"