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.