Lost a few customers like that,
explained I have cleaned them for 2yrs like that
and they never said anything before.
3 reasons for there being like that I have found.
1) they feel you earned there money to easy
2) they feel job is half done unless you dry them off with blade or cloth! "Ain't you going to dry em off)
3)compare your job to there job and don't like you earn more than them unless you sweat and risk your neck up a ladder.
keep your dignity and say see you around and carry on.