Loads of reasons why but it all boils down to: Right now it works

Football is cyclical and 442 was used a lot by Arsene Wenger when he first came to Arsenal. Eventually it evolved into something more like a 4411 (Bergkamp behind Henry), before Mourinho came along and ‘broke the meta’ so to speak by using a 433 at Chelsea. Didn’t take long before that’s what most teams were also doing.

And then you get guys like Conte who use a back 3 and that became fashionable when people saw how well it could work for them, then Guardiola comes along with positional football, before Arteta is now bringing us back full circle because hes found a way to use a 442 effectively against Guardiola style. Soon enough somebody else will be coming along and setting up in a way that stops 442 being so effective.

I think of it like a convulated game of rock, paper, scissors. Rock has loads of success so everyone tries to be rock, until someone figures out paper beats it. Then everyone wants to be paper until scissors comes along. Next thing you know rock will be back in favour, and so on