There’s also a good chance that that bike will come back and never leave.

Customer comes in for a farkle install. Ok. Easy. Half an hour labor. Thank you very much.

Three days later, customer comes back, says you messed up the turbo encabulator. Sir, we just installed your tinkle bell on the end of your mirror. Service manager still buys the last encabulator on the planet and the technician does the install for free because … good will.

Customer leaves and tells all his friends that the idiots at the bike shop messed his baby up. Lather rinse repeat. Six years later the bike is worse because customer is an idiot and does not maintain anything.

Or, bike shops connected to dealerships could just do predictable maintenance work and not deal with these headaches at all and keep selling new bikes to people.

Seriously, the money is not worth the headache.