I had a literal standup battle the other day when everyone wanted to give me a seat on the bus (heavily pregnant) but I had a support belt on that would have had to come off, and by the time I’d sat down I’d need to stand up again and it’s a MISSION; it was me vs a bus load of chivalrous people. Felt I was letting the side down for pregnant people everywhere because next time they might not offer.
I'm sure they will @stuntbubbles, people usually do as OP found with the man who gave up his seat to her and her toddler. As I said, I probably would in that situation unless my feet hurt in which case I'd hope someone else did the chivalrous thing first.
My mum travelled on the Tube until two months from her death aged 90 and a half. People always gave her a seat which gives the lie to people who say how callous Londoners are.
She was very fit and strong but she was 90 and a half so always accepted unless she was getting off in a few stops and it was safer to hold on tight to a rail rather than risk wobbling her way on a moving train to a seat and then back again. Then she would graciously decline. Bit like you and being heavily pregnant.
It was funny to see how disappointed people were to have their kind offer refused. And it was kind of them. I am not mocking. It's just that people don't always understand. But I am sure that never stopped them offering again. Well, maybe one or two but there is no accounting for weird people and I'm sceptical about people who claim they never offer because they did once and were rebuffed.
I was offered a seat on the Tube on Tuesday evening as soon as I got on. It was a young east Asian tourist, possibly Korean. It might have been because people from his part of the world always give up their seat to women or maybe I looked especially decrepit. I thanked him and declined. I was getting off at the next stop. Perhaps other people might have but I was standing next to him and he was first.
In my experience of public transport and other situations most people are quite nice. I offered to help a disabled man reach something in the supermarket today. He said there was no need, he could stand but found it easier to get about on his mobility scooter. I will offer again for the next person I see in a wheelchair or with a toddler on the train or in a similar situation.
I might even post about it but I won't do a reverse like the OP did. That is just tiresome. Especially when you got a seat without asking anyway.