Seeing as NYC is one of, if not the top location(London, Paris,as well)in the world for terrorist activities I’d say that increased levels of security are justified.
Trying to thwart and being prepared for bombs, biological/chemical or other attacks at large gatherings is prudent, imo.
There was this event on 9/11/2001 which was preceded by another event on 02/26/1993. Maybe those, and other attempts to inflict mass casualties that were stopped, have something to do with it.