But you don't have to give $12,000 to each, just enough for them to get to $12,000. A majority of them seem like they already make more than half that much, so let's say on average we give around $5000 each.
If someone is making $11,000 and gets $1,000 free, what's the incentive to quit working and just get $12,000 free? To avoid that problem, you need to structure any such program so that getting paid more to work actually leads to having more money, If indeed $12,000 is the desired guaranteed basic income, then perhaps half of the difference between what they make and $24,000 would have a chance of working as intended.