What happens when someone inevitably spends their entire income on non-essential expenses, or bets it all on black, or gets talked into making a bad investment, leaving them with no money in the bank? Do we just tell them, "well, suck it up and get a job"? "Sorry, you can't feed yourself because you made your choice on how to spend your money"?
Replacing all other entitlement programs with a cash handout is a political non-starter.
Most entitlement programs in the United States are based on the poverty line. Currently that number is $11,770 for an individual. Working 40 hours a week you'd receive $15,080. Thus a great many working individuals simply do not qualify for much government assistance already as they not only receive more than minimum wage but they also work more than 40 hours a week.
My point is the way the system is currently designed punishes the working poor who have managed to make a life for themselves and rewards those with part time jobs, many of whom have chosen to not do so. If framed in this way I estimate that this would not only be politically viable but the party who proposed it would win in a landslide.
I do think that some aspects of our tax system could be reworked. Creating a wealth tax and removing income and other redundant taxes seems to be a popular idea[1]
[1](http://www.nytimes.com/2012/11/19/opinion/to-reduce-inequali...)
Think about it like this in the US: Imagine giving everybody a basic income and eliminating minimum wage, social security, medicare, welfare, and so forth...
Naturally some people would become wealthier (paying down existing debts) and some people would become poorer (spending money more rapidly and increasing their debt burden), but these are personal decisions.