Because maintaining and advancing those things takes
work. If you work less, you won't be able to afford that Internet subscription and $1000 in hardware to access it, you won't afford the $3.30/gal gas for commuting, you won't afford the iPhone with data plan, etc. Your employer will have to extend deadlines and cancel projects because you (along with everyone else thinking less work is a great idea) just aren't producing 4x your new relaxed hours, and thus tech won't be advancing nearly as fast and may not even keep up with the stresses of growing population. Doctors cut back their hours, and people consequently die in the ER. Lacking the now-deceased cell tower maintenance guy, your cheap cell phone doesn't work any more, and the reduced-hours landline installer for your area is booked for the next 2 years. Wanting to find a clever solution, you realize you can't access Wikipedia for a simple but very relevant factoid, and have to go to a local garage sale to pick up a 20 volume 10 year old encyclopedia - and carry it back, because you can't afford to repair the car.
The Red Queen was right: sometimes you have to run (work) hard just to stay where you are; slow down, and you'll go backwards.