Simple economics, resources are scarce.
lol this is why it is hard to argue against multiple opposing points. You say resources are scarce. Koop says we have enough resources for 100 billion people :P
And if everyone has the same money as everyone else, what incentive do I have to go be a good doctor, lawyer, whatever.
The incentive should come from passion. I would still happily be a doctor or lawyer because I found the subjects in those fields interesting when I studied them. People with passion for sports would still play I think. A lot of people do things with their life because they are passionate, despite the fact that their passion won't make them rich.
Yes, I realise that a lot of people would bludge and freeload. :P But that's why I said it is good in theory, but doesn't work in practice. Imagine if everyone went and worked instead of bludged and freeloaded. They could work in fields they are passionate about without worrying about financial obligations like whether they will meet their rent this week or not. Life would be awesome :D Perhaps you could simply make it a requirement to work in order to get the free stuff. You can work in any field you want, but you still need to meet the quota. I think that could drive people to work.