Erik brings up the question as to why we still have 50,000 troops in Germany. It's a legitimate question and while I have no expertise in answering the question, I would like to address some of the issues involving my experience growing up for a portion of my childhood in that environment.
My dad was a civilian employee of the US Army and we had the pleasure of living in the Kaiserslautern Military Community on two occasions (my parents lived in Germany by themselves for three years on a later occasion). I graduated from Kaiserslautern American High School in 1974 and would consider my experience there one of the formative experiences of my childhood and adolescence. Notwithstanding the physical distances, time, etc. that separate us, I still maintain contact with a number of my friends from that era.
As wonderful as it was, these things do cost money and time. While what is normally focused on are the issues involving the direct military expenses (barracks, equipment, facilities), what is rarely discussed is the amount of support ifnrastructure developed in the area. Kaiserslautern is an excellent place to address this issue as it was when I lived there - and still is - the largest American community outside of the US.
What essentially took place was that a small American city is relocated outside the US. In addition to the schools, the scope of which can be best examined in detail at this link, there are any number of recreational facilities, including snack bars, restaurants, officers clubs, NCO clubs, enlisted men's clubs, libraries, PXes/BXes, commisaries, swimming pools, gyms, etc.
The school facilities were excellent. I went to my first integrated school at Landstuhl Elementary (my first one in the US was in the 8th grade in Alabama). We went on excellent field trips: Speyer am Rhein, Worms, museums in Darmstadt, Frankfurt and the Gutenberg Museum in Mainz. We had a sort of Outward Bound lite program, put on plays, had athletic teams, any number of student activities programs and special buses to take us from school back to Fliegerstrasse, for after school activities (play rehearsals, athletic practice, etc.) where I lived in downtown Kaiserslautern.
Movie theaters ran first run films some six months after release in Vogelweh, Ramstein Air Force Base, Sembach. and in a number of other facilities. Housing was built for families, "teen clubs" for the children of residents to play ping pong, pool, foosball, have dances and hang out. For those not able to find space in housing (usually married enlistees), housing allowances were given to ease the expense of living on the local economy. Not to belabor the obvious, but schools also need teachers and adminstrators and there were plenty of them in Kaiserslautern; not only for the schools in the immediate area, but also for district administration.
For two summers I worked on bases: once at Panzer Kaserne for the Rheinland Pfalz Support District and once at the now defunct US Army Medical Material Center in Einsiedlerhof. I worked with a number of local nationals (i.e. Germans) and spouses of military personnel. Organization Day was always the best time: not having to work and plenty of burgers!
I would not begrudge any of this for the military and civilians working under these circumstances. For me and my family and most of my friends, the experience was beyond merely memorable, but there were plenty of people who were always homesick or who rarely left the posts or bases. None of this is accomplished for free and I mention all this to give you a sense of what is involved in creating these sorts of communities. Kaiserslautern is an extreme example of this; few facilities these days even come close to its size.
Indeed, if this Wikipedia entry is correct, the number of facilites that have shuttered since I lived there nearly forty years ago is impressive.