you need to do a bit more research
Nobody said it's the same as whatever scheme you have in your head. Maybe it's a new idea for you but not so for some of us. It's been around since "Utopia". A few centuries.
I have read about a few schemes over several years. This one is very different, because the amount of money is far higher - by a factor of 4 or so, than trial schemes all over the world. You can't use their conclusions to support this one. For example, a UBI of 400 Euros didn't discourage people from working in FInland - but then it's not enough to live on, is it? £1600 a month, each, IS enough.
Even where it's much smaller, one reason the trials stopped is because it's perceived as money for the wrong people. At £1600 a month, it's a slob's charter.
It ( if like some other schemes) replaces child benefit, income support, JSA, NI ,other state benefits (UC?), and pensions. So
it's clearly not fair, apparently. So it's just "benefit". But not matched to those who need it. Bad.
There is merit in not having anyone so poor they have nothing - which happens now when they fall between different schemes for odd reasons. Like some zero hours contract workers - (a scheme which should go.)
If you leave SOME benefits as additions, the UB model is out of the window too and you have huge discrepancies and errors.
If everyone is appreciably better off, prices rise, because they can. I will charge you more for fitting a boiler/rewire/insulation because you can afford it, can't you? That pushes us back towards where we started.
If I need to employ you, I might decide minimum wage is good enough because you aren't broke. Same effect.
Another idea that gets regurgitated is negative tax. If you're on benefits but earn £100, you'd get
extra from the government, to encourage you to work. Sounds great, but of course that would tail off so people would then feel less incentive to work more, and, as above, employers would know all about it.