One reason why Mastodon, being part of the Fediverse, is great, is that whenever the next big thing pops up (let's say the Mastodon of The Future), and it stays within the Fediverse, we will all stay connected. No more "starting over" our networks from scratch.
We all have friends and family who are like "so you want me to switch to Mastodon now? Last year it was Signal, and before that Telegram. I can't be starting over all the time. I'm sticking to Whatsapp and Twitter". Now they won't have an excuse anymore. After switching to the Fediverse we never have to start over again.
For example: if at some point all the cool kids move from Mastodon to Lemmy (the Fediverse alternative to Reddit), and you want to join them, you won't have to lose your Mastodon crowd (and start all over again, isolated and lonely): your old friends can simply stay where they are (on Mastodon) and follow your new Lemmy account on Mastodon.1 (And it of course also works the other way around: if your friends move to Lemmy, you won't have to necessarily join them to keep following them. You can follow them from Mastodon.)
This is one of the fundamental ideas (and selling points) of the Fediverse: instead of using network effects (that kind of emerge naturally as people club together) to prevent people from escaping to alternatives (like e.g. Instagram, Twitter, Tiktok, Snapchat etc. are doing), the Fediverse enables and even promotes connections with alternative networks (across platform boundaries). The only precondition is that these alternatives are equally open to other networks.
I know that there is always this risk: every attempt to create a standard to bring together all other standards often just ends up in yet another standard. But let's choose a foolhardy pursuit of freedom over a cynical embrace of commercial captivity.