Magic things are dumb therefore sinks are dumb.
Showers and washing machines should also not be infinite use.
Vector for sabotage (spiking, scalding, luring)
Vector for diseases.
Extra movement path for vent / pipe crawling critters.
Plumbing exists in a minor form in SS13.
Additional maints structures, maintenance burden for longer rounds.
Opportinity for new mechanics and interactions with gasses, chemicals, atmos and engines in general.
hygiene? (suggested by Dynexust)
Mass production but better.