Firstly because people would abuse it and secondly because appearing to be a good prospect for mating turns out to be something that gets selected for.
SgtSpike, that's simply not true, humans have existed for thousands of years by caring for their selves. Is there not enough food? Grow some yourself. These things called regulations prevent us from caring for ourselves.
Who actually dreams to play video games 24/7? I loaded up counter strike source, the other day, and it just wasn't the same. Most people grow out of these phases and find something they enjoy that also contributes to others.
Of course computers could have been created without currency, do you have to feed your computer dollar bills to turn on? It's all metal. It took the push of a little bit of greed to get technology as far as it is, in today's society, but it could have happened without.
Regarding electricity, that in no way destroys the environment, unless of course, we use coal and oil to generate electricity rather than clean, renewable, hemp biodiesel.
Technology is very much possible without money, if you enjoy technology, you can work on it to further develop it, with like minded humans.