my point is most _rented apartments_ are not setup like that and do not provide a reasonable path to have it most owned apartments also are not build in a way

my point is most _rented apartments_ are not setup like that and do not provide a reasonable path to have it most owned apartments also are not build in a way where it's easy to retrofit. So if you don't do a "in depth" renovation anyway, its often just not a good option from a financial POV. Especially if you have to reroute plumbing (for the floor level wet room sink), especially if beton floor or pre-existing floor heating is involved.