Obviously for some events like the royal jubilee, trooping the colour etc, they had no choice but to stay, and didn't they seem to hate every minute of it lol Harry seemed to get on with that stuff just fine before he met Meghan. Weird.
This is what fascinates me! Over the years of observing Meghan's behaviour, it strikes me that the common factor is lack of ability to be calm, still, or to just concentrate quietly. Or, in more active social situations, to blend in with others and allow them equal prominence, or an equal share of the limelight/attention.
She is utterly lost when she is not the focus of everyone's attention - not an endearing trait, but I've come to believe that she just cannot help herself. I agree that there may have been many reasons for her not taking her place at a table at the hospital event, but I bet sitting with others and making conversation for a couple of hours, and possibly listening to speeches MADE BY OTHER PEOPLE is probably beyond her.
I knew someone like this once, and she was absolutely exhausting company and totally unrewarding as a friend. She had no interest in anyone but herself, no self-awareness (would talk incessantly about herself, but then moan about anyone who did the same, even for a few minutes, as being boring (with no sense of irony). She could not cope with being alone and if you went anywhere with her, she'd chatter mindlessly throughout - films, theatre, concerts - she just could not focus or listen or concentrate. I bet Meghan's like that - and I confess she fascinates me as a psychological study. Just look at her on the balcony that time, when Harry had to tell her to look ahead and shut the hell up not once, but twice!!! And even then, she had a defiant look.