I mean, it was obviously a hyperbole, that they need it as much as air, but TikTok (like many other social media platforms) has addictive qualities.

The first ingredient for addiction is to somehow cause joy without requiring much effort to be put in. Whether that's heroin, sugar or funny memes, short-term they will cause happy brain chemicals to be released.

If you're completely abstinent, you'd need to put in work + achieve something, to get those happy brain chemicals, so it requires more effort.

(That's only short-term. Long-term, having achievements to look back to, can instill more happiness, but it can be hard for our brains to conceptualize long-term.)

One way in particular that TikTok et al are similar to an addictive medium, is that scrolling through posts is a bit like a slot machine. Since the order of posts is largely random, you never quite know, if the next scroll is going to have the funniest meme, much like each pull on a slot machine might have you winning money.
As such, even if you're 'losing' most of the time, you'll just keep scrolling, hoping for that random win.