I've been meaning to ask someone about this for years. FT seems like the place to ask.

AT LGA the aircraft stops short of the arrival gate and the captain says "we have to have a tug take us the rest of the way in."

Why? Is it really too tight to park without assistance, or is this an example of union make-work (like the railroads were forced to keep firemen and cabooses long after they had become obsolete)?