I'd argue those have a different enough dynamic that they're easier to compartmentalise separately from regular social interactions. Obviously there's bound to be some crazy hag out there who thought Elton John signing a poster for her thirty years ago turned him straight and he's been leaving messages for her in his songs ever since, but fanmail exchanges, radio call-ins etc. are less immediate and more controlled, so they have much less in common with normal conversations with your actual friends than having regular interactions with a streamer several times a week; while on a mainstream celebrity's end they're much less likely to see the same people showing up time and time again than a streamer (and if they are, they probably have reason to call security). It's easier for someone to get their wires crossed with livestreams, especially if their frame of reference for irl relationships are limited.