The government can barely afford a benefit for the unemployed, they definitely cannot afford to pay everyone one!
Plus, as arsenal said, it doesn't exactly encourage people to work. A lot of people would be content to just live off their UBI, and not contribute. I know that kind of happens now, but at least with a benefit there is a theoretical scope to pressure people in to working rather than bludging.
Erm anyway this is way off topic. How did it come to this? Jesus wept.