Some Muslims, who may or may not think they are better than others, Astaghfirullah of course, say "Allah bless you!"
And they say it before, after, or in addition to saying Salaam.
And they may -- or may not -- think they are being cute.
At best it is a redundancy. For, that precisely is what "Assalamu Alaikum" means:
"Allah Bless You All!"
At worst, it may be some kind of an effort, no matter how unconscious or naive or foolish, to outdo Almighty Allah himself: Wanting and trying to do things better than Allah can do.
And better than Allah already has done -- way before they and their fathers and mothers ever showed up on this earth.
So, Allah did it before them. And Allah did it much better than they ever could.
For, Allah's Salam beats your "Bless You!" or any variation or modification or improvement thereof, hands down -- anytime, any day.