IME it’s not just about people wanting to move out faster; but in general it seems that most places get offered to friends/coworkers first, just as a gesture.

IME it’s not just about people wanting to move out faster; but in general it seems that most places get offered to friends/coworkers first, just as a gesture. Often having a Nachmieter is handy because you can sell them any of the furniture (or appliances) (…or entire kitchens) you no longer want, and they can also take over responsibility for any modifications to the place you’ve made. I once lived in an Altbau that had very high (~5.5m?) ceilings, and the previous tenants added a lofted bed to the space. By finding someone (me) to take over the contract, they didn’t have to remove it and fix the holes in the wall etc, and the next tenant after me also got to keep the bed setup.