I feel like beards are a reaction to the clean-cut look of the 1980s and 90s. The mainstream aesthetic was clean-cut brutalism, from architecture to facial hair. People in media lived in almost empty spaces made of concrete and hard lines. Even the grunge/plaid look of the 90s featured beardless dudes with a hint of stubble.
In the 2000s, there was a reaction against that. People looked for alternatives. Hipsters grew beards and mustaches. Instead of IKEA catalogs, movie characters lived in cottage-core wizard hangouts or busy apocalyptic shelters. This will continue for a while.
In the next decade or two we're going to see a reaction against that. Politics are going to get funky and I think that'll help get us back to clean-cut and brutal. But here's hoping for a hirsute solar-punk future. Given a choice, I'd take a 1990s-style perfect shave in a solar-punk future, but that's just me.
Fashion is always cyclical. There are loads of guys with beards today, but so many look awful, unkempt, and untidy. Kids today will grow up seeing those awful beards and decide it isn't for them after a couple attempts. A good beard takes just as much effort to maintain as a clean shaven face, which the next generation is going to experience.