More and more people do that, but they don't get mindshare, mediatic exposure. The most common images conjured when one talks job are:

* unskilled people piling on minimum-wage jobs to avoid bankrupcy;

* start-uppers who clock insane hours, in the hope of becoming filthy rich through Google ads revenue on their new "AirBnB for pets" or whatever;

* IBMers (do they still exist as we picture them BTW?);

* jobs of limited interest and impact, done half-arsed if not worse, as seen in tv shows like _The Office_.

The skilled guy who goes part-time because he makes enough working 3 days a week to enjoy the 4 remaining ones exists, but he's not thought about. When his female counterpart is considered, she's typically seen as sacrificing her career for her kids, rather than buying herself time by not working more than whatever she needs to earn.