[ETA The OP asked about the experiences of others.]
I'm an only child. My mother outlived my dad and she also outlived her siblings. Her nieces and a nephew did occasionally visit.
I was also my late husband's carer. I've probably said too much about that on these boards, but there was little or no support from his adult kids.
They'd stay with my DH's ex and whichever partner she was with and meet us for a meal. Latterly, we always had the meals at a local restaurant because of my workload and the fact that we'd be expected to invite the ex. (Long story.) DH always paid.
One of them was supposed to stay with us one time, but didn't show. DH phoned his ex, to find that his daughter and her partner had gone there instead: "Mum thought we were staying with her, and I couldn't hurt her feelings."
When I became ill one time, I phoned the daughter to make it clear that DH would need care if anything happened to me."You're not thinking of leaving him are you?"
DH had three extended hospital stays over the years. He got one half hour visit from one of the kids. It was the same when their mother was unwell, actually. It was all left to her then partner. No hospital visit.
When she needed a day op, I was the one who volunteered to take her to and from hospital. (Her partner had died.)
Latterly, DH warned me that the kids wouldn't come to his funeral. I told him that he was wrong. He was right.
It was lockdown, tbf, but at least one of them could have managed. They did attend the funerals of their mother's two partners to support her. By lockdown, she was with another partner.