I don't know whether this can be classed as 'trivial' because I can see how it could potentially be quite damaging, but.....
Parents who try to live their unfulfilled dreams through their children.
This takes various forms. If I walk through the local park on a Saturday morning, I see fathers shouting at their children while playing football, acting as though they're in any way qualified to give managerial/coaching tips. Just let them enjoy the game and develop at their own pace, for crying out loud!
I was a 'victim' of the middle class equivalent. If my mother is honest with herself, if she could have her time again, she'd have tried harder to pursue a career as a classical musician. She had piano lessons that had to stop at the age of about 14 for certain reasons.
Then, when I was about eight, she insisted that I learnt the trumpet, and that it would do me good. It was fun to begin with, one lesson per week at school, 10 minutes' practice per night, county brass band on Saturday mornings.
When I began to make progress, she started paying for me to have private tuition every week, as well as Wednesday night band and secondary school band.
Frankly, I began to hate it. Some of the teachers were bullies, I didn't like some of the children it brought me into contact with and there was a real snobbery amongst the parents. Practising for an hour and a half per night (minimum) was a real chore when I'd just had a day at school, which also involved a two hours per night homework policy.
I pleaded with my mother to at the very least let me cut back on the commitments, and certainly to stop seeing the one obnoxious teacher, but she was having none of it. She saw it as her job to 'push' me.
My hobby was ruined. Following a period of illness at the age of 12, coincidentally around the time my parents separated, I cut back to school brass band only, and stopped lessons completely. Within a couple of years, I'd stopped altogether.
I see this sort of thing going on in various other contexts as well, especially among the middle classes and their children. There's a very big difference between encouraging and supporting your children, and the sort of 'helicopter parenting' you see with parents trying to live out their dreams through their children.