Sounds like you get more than your fair share of entitlement mentality. Some people believe they deserve things which are actually a privilege, and to sensible people they look stupid and spoilt when things don't go their way. Doesn't look any better when they also fail to even attempt to think a problem through for themselves and come up with a solution. They are convinced that everything that goes wrong is someone else's fault, and someone else should fix it.
Life is the best educator for these people
We do have an entitlement menatility representation, but the "ever since" factor applies to all workshops and all customers.
We had a "weekend warrior" in a Prado (he's a bogan tradie, and a total knob) bought his car to us for a service and repair a broken rocker cover gasket bolt (which he broke trying to fix the rocker cover gasket leak himself). We had never seen him before, and the car has been around the world twice by the looks of it..
Couldn't fix the broken bolt without serious work (he thought it'd be "a 5 minute job") - it was at the back of the engine near the firewall - can't be easily drilled out, so reported that, and reported 3 oil leaks - one was a transmission leak.
He calls us up 3 weeks later to complain about an oil leak - "what did you blokes do/not tighten up...it wasn't leaking oil before you serviced it".
Yer classic "ever since". I suggested he bring it back so we could reinspect it to make sure everything was tightened up correctly etc, but I also suggested it was probably one of the 3 leaks we reported last visit.
He is not an entitlement level person per se; just a knob who was "trying it on" for us to fix his peice of cr@p car for free...happens a lot.
The previous two examples are yer standard retired old bloke (maybe a pensioner, but possibly self-funded...retired from Thomastown down to the holiday house, type scenario) and the other was yer standard 40 year old Aussie housewife with the two kids.
From my experience, car ignorance/laziness favours no age, race, wealth level or gender.
We have younger women who know more about cars than most younger mechanics, and 40 year old blokes on 6 figure incomes who couldn't find the dip stick.