It does happen occasionally, but DB tends to run, maintain and sometimes upgrade its successful (~reliable and widely introduced) rolling stock until it falls apart or is grossly outdated (40+ years old). Rail passenger numbers are increasing, so there is no need to sell stuff to downsize.

The Flixtrain company uses 40+ years old IC (intercity) cars - they have no air conditioning and it's really loud inside with open windows, especially so in tunnels. That is the kind of stuff that DB sells.

There is even a website just for that: https://www.db-gebrauchtzug.de/r/gbzp/gbzp/home?session=2228...