I think New York is one of the last holdouts against Discount Tuesdays. Here in Sacramento, Regal wasn't participating in them until sometime this year, but when when Cinemark followed the suit of Cinema West, they soon had to do so as well.
That's what I meant about 'market forces'. As soon as one place in an area goes to Discount Tuesdays and the other theaters in the area start to suffer lost business, the rest sooner or later fall in line.
It also helps that it does seem to be profitiable for them. I can't really say if it's added to box office gross overall or if it has just shuffled the M-Th pattern a bit, but it does appear to be here to stay.
====
One other note, every single theater here in town makes an exception on Discount Tuesdays for films that are opening that day or are having their Preview Night. Gotta pay full price for those. No fools they. IIRC, some places tried to exempt a movie in its first week from Discount Tuesdays, but that didn't stick for long. Can't imagine why.