A plasterer will clean, oil , protect his skimming trowel. He will not allow anyone else to pick it up, never mind use it. He can NEVER buy a new skimming trowel, even though his skimming trowel was bought new for maybe 30-40 quid. But he won't clean out a £350 drill. Why? Maybe because if it breaks he can fix it, maybe because if it breaks he can buy a new one?
Or maybe because that's the way it is when you are a plasterer.
Because once he has finished with his trowel the muck on the mixer has bloody well set!