It's the most popular take-away snack food in Southern Germany, so yeah, totally common!
It's also the most stereo-typical Bavarian food that I know of, besides Weißwurst.
In my city there are even booths scattered all over town selling nothing but sliced pretzels filled with dozens of different topings you can choose from.
The butter one is still GOAT, though.
You can get it in every bakery.