Yes, there are plenty, try google.de and type in "billard" just as i typed it. Depending on what you are looking for there are fun rooms and serious rooms. As I remember it there is not much in Stuttgart proper but there are some nice rooms in the surrounding towns with some serious players.
Same thing for Frankfurt proper. Lots and lots of rooms within 30 minutes drive but not much in the city limits.
Do like I did last time I was there - rent a brand new Mercedes coupe and enjoy the autobahn between rooms. The funny thing is that I opted for a cheaper car although I wanted the Mercedes and when I got there they upgraded me to the Mercedes for free because they were out of the cheaper cars! Sometimes Karma loves you.
Here is a link to all the places to play with real pool tables and real pool.
http://dbu.billardmanager.de/public/pub/showPubList.php
A Billard Cafe is a pool room
A Vereinsheim is club house - not always open to the public.
A Gastestatte is a bar/restaurant - likely to not find much going on there.
The other kind of place is a video gambling place with pool tables. Generally there isn't much happening at places like this pool wise. Sometimes you can find money games of last pocket 8 ball at these places but beware of tricky rules.
There is plenty of pool in Germany but you need to know where to go. The list I gave you is the list of all registered places to play league games. 7-Up in Stuttgart proper is an alright place to go.