Just like nobody ever did their homework? Because after all, nobody sees you not do it and nobody cares if it's not done when it was supposed to be done.
And nobody bats an eye when the feature you talked about in the previous standup or meeting somehow mystically never materialized in the project's repo... nobody cares that you never were there to answer your colleagues' needs.
Or, you know, maybe people can actually get things done even without a surveillance camera monitoring their butt in seat.
The good thing about remote work is that results and communication (i.e. things that matter) are the things people see.
And that is different from how people game any other metric how? You realize that boss buttons and quick alt tabs are a thing with butts-in-seats, so that's not game-proof either.
For all the rhetoric about enhancing communication, I'm pretty sure open offices are mostly about getting people to police their coworkers.
Add 6 hours to that and that pretty much sums up how productive most people would be with the freedom of working from home without being monitored.