Yeah social networks seem to be 'generationally sticky'. This is probably just network effect shit. You and all your friends are on instagram and use instagram together as your 'main channel'. Tik Tok comes along, some join but some don't. But the next generation they join Tik Tok as their 'main channel' .. the process repeats.

Essentially:

Facebook = boomers Twitter. = genx insta. = geny ...

(but for some other shorter generational definition)