There's already plenty of people working only 4 days per week, lots of times they do keep a low profile though.

The more workers who do start performing the shorter weeks, the more of the remaining workers will have to work more days per week than they are doing now.

As it stands your odds of pulling it off individually are probably better than waiting to see if it becomes adopted by the mainstream.

So there is probably widespread inertia in favor of the status quo.