Free time! And then what?
Okaaay, let's wind this scenario forward.
FF to the time when we have all we need in terms of physical stuff. Hungry? press a button and a robotic shopping cart will deliver the hot pizza of your choice. Thirsty? Same cart will bring you whatever carbonated beverage you desire. Repeat from age #1 to age #99, daily. Every day. For your whole life. For ever. All the friggin' time. Just press the button. That's it. All you do is press the button.
Next to "the button" is another button labelled "Kill me now". You can press that one any time you please, too. Maybe that one would just about help us avoid a Malthusian disaster.
The basic problem is human nature. To start with, we only value what we earn. Whether it's the satisfaction of standing back and thinking "I made that", Whether it's the knowledge that you're a "provider" and other people respect and depend on you. Whether it's saving up to go and see that band you like.
We also earn a status from being in work, whether it's productive work or merely IT (which, truth be told hasn't really improved the quality of life much at all. It certainly hasn't done a simgle dam' thing to get the country, or the world, out of its current recession). Meet a stranger and one of the first questions they will ask you is "what do you do?" Hands up anyone who hasn't embellished their answer, even just a little bit.
So, work is necessary. Not just to get us the stuff and the mental state that we value. It also sets our standing in society. Even if work became unnecessary in orer to get us the pizza de choix, we would still wish to fill our time, just to give ourselves something to talk about at all those soirees that our excessive free time would require we attend just to fill the empty void before bed.
Plus work allows us to get away from our children (and them from us).