Young people (say under <20, those that actually don't use FB[1]) have no need for FB in the first place - they see their friends every day in school, in parascholar activities and social gatherings. Once you are out of school is when the model gets sticky, FB becomes the bridge between you and your social life for most people - it really is between FB (+Insta/WA), phones and e-mails, and guess which holds the most contacts for most people [speculation/projection]. Snapchat and TikTok and great competitors for their share of online time-spent, but they won't be able to replace FB's utility for keeping in touch with people you've met once they need such a SM.
[1]: https://www.statista.com/statistics/187549/facebook-distribu...