They are absolutely everywhere since last year more or less, but everybody (esp. cashiers) is always dumbfounded when I use it and it works. Also some of them try to handle your card for you "to insert it in the right way" and since my German is still rather basic I then have to weigh the potential time waste of explaining it's a contactless card with the extra 4-5 seconds for the chip transaction. But I guess that part doesn't really apply to locals.
("kontaktlose karte, nicht einstecken" but they don't listen the first couple times)
Some stores have fucked up the speed of it though by first checking for your store membership account on the card which ruins the flow of the transaction. Often forcing the whole thing to be repeated. It's infuriating.
On a short trip last month, I surprised a couple of merchants by paying contactlessly with my foreign (EU) card.
That's almost always faster than paying by cash, since there's no need to count the money or make change. The exception is when the cost is €20, and I can hand over a single note.