Why hasn't the four-day work week caught on?

[youtube https://www.youtube.com/watch?v=fE02HI13wso&w=620&h=315] I've written about the idea of a four-day work week twice before -- here and here -- and I just wrote a piece for Vocoli (might be online tomorrow) on the same topic, so I've been thinking about it a lot recently. I've also written before about the idea of ROWE -- Results-Only Work Enviro…