I think once they meet their partner, they let their friendships die out because they have their partner now and don’t need anyone else. It’s happened to me and several people I know in rl.
I’ve also found people to be helpful on trains towards people struggling. I’ve seen men offering to help mums carry the pushchair down the steps, my sister had passengers help her with the pram on board the train, someone offered to help me with my heavy suitcase and one of my friends was struggling to get off the train due to her disability so a lady offered her a hand. Separate experiences.
Mind you, I expect Mumsnetters wouldn’t accept help on a train and be a martyr.