I agree that it's dumb to have to buy a new kitchen when moving in (and tear it down when moving out). In most cases, though, you talk to the next person that moves in and, depending on the quality of the kitchen and social factors, sell it to them or just give it away. That is, when it's not part of the lease, which does exist in Germany, even if it's not mandatory. Student housing, for example, is usually fully equipped.