Of course some people are just assholes, but ime, this rings 100% true.
My mum (born 1948) was brought up to believe that being self-centred was the worst thing you could be (closely followed by being fat, of course 🙄). I had a lifetime of "you/we don't matter, it's all about other people". She 100% applies this to herself as well, wasn't just me. Having ANY self-esteem is seen as a character flaw. She was careful to praise me, but it had no impact because of her constant self-flagellation - to a child's mind, if mum is so awful how much worse must I be?
I'm nearly 52 now and unsurprisingly I still have terrible confidence issues, always err on the side of pleasing other people, spent 25 years in an emotionally abusive marriage, etc. I have also been very overweight (size 16-22) for most of my adult life.
I have tried SO hard to instil confidence in my dds, but I have so little in myself that I know it's an uphill battle. My mother would very much prefer all women, esp her relatives, to be self-effacing to the point of being non-existent. And THIN.
In her mind, praising/standing up for us is for other people to do, NOT ourselves. Even faced with the immutable fact of many, many people not being like that, therefore by being how she thinks would expose us to appalling treatment in every part of our lives, she insists that makes no difference. Self-effacement to a fault is simply 'the right thing to do'.
She does get angry when any of us are treated badly, not that she'd ever do anything more than rant privately, she'd never say boo to a goose outside her own four walls. But she still can't cope with the idea of any words (or, worse, actions) that might mean we're standing up for ourselves.
It's incredibly sad and a shit legacy.