You underestimate how lazy humans get if they don't have discipline and/or pressure.
People think that company profits on a per-employee basis are something like a factor 10. In practice, for the best companies in existence (think google) it's a factor of 3 or so. For most companies it's much lower 10% would be a lot (hiring is already very expensive, just try it). This number is called efficiency of the economy and it's an upper bound on how much more money you can give any significant group of people (assuming labor costs dominate, which is currently true). Of course you could give them more by law, but it would simply result in massive price hikes for everything until we're back in the current situation.
Or, as I think will soon be happening, robots will do it.
The current welfare programs are already funding those people, so let's replace it with one that covers everyone instead of those who enrolled.
Also, how can you give without first taking?
BI is supposed to cover food and simple housing, people that want to travel, have a large house, or have hobbies will probably need at least part-time jobs to cover that, their incomes will be taxed.
The problem is getting over the idea that some people would be freeloaders, but again, if the total cost is less than the current cost of welfare, it's in our best interests to switch.
I'm not certain that it will work or that it is a good idea, but the counter-arguments seem to be 1. people irritated that they'd be forced to pay for the lazy and would rather lazy people have a shitty life than have less welfare expenses for the state, 2. people who assert without a scientific study that the majority of other people in absence of a job wish to do nothing but watch TV all day every day, and 3. people who just flat-out construct strawman arguments about lazy people having parties all day every day at the expense of the state.