I can't speak for the other old timers preference for the old game, just for myself.
My brother was friends with Dave Arneson back in the formative days of D&D . As a result I cut my teeth on the early version of the game, and later I was heavily involved in playing AD&D.
I'm glad D&D is still being produced in some form, but I don't really care for the game as it is now, and I won't resort to playing the new D&D so long as I have the books, materials, and fellow players necessary to play a superior(imo) earlier version of the game.