I like the idea of everyone earning a set amount and then working for more, but then the system breaks down, because nobody wants to contribute back.
There are more rewards than money.
Those who don't contribute will be considered leeches just like they are today. Normal societal pressures will still remain, being part of the group, being a good citizen, and contributing to society are part of that. Many people already donate their time and effort to running community groups and clubs for free to improve their social standing, rather than monetary gain.
People already change the way they act in response to societal pressures to conform, and so long as the rewards for working are good enough then people will want to contribute. Mincome isn't about everyone living like kings, its about removing the bottom end off poverty, and allowing people to enter into working arrangements that benefit them, rather than being forced to take a bad job that exploits them because without it they cant afford to live.
Everyone wants to be a millionaire, but society can't support that.
Some people want that, some others seem reasonably content to live a comfortable life with their family, or just want to pursue their passions whatever they may be.