Not true. The 'B' in UBI means 'Basic'. UBI wil pay your rent, utilities, and food, but not much else. Now, there are some people that are willing to just exist on only the bare minimum, but that's a significant minority. The vast majority of people want more. There will be plenty of people willing to do minimum wage jobs to top-up their UBI so they can afford extras like holidays, nicer phones, meals out, etc...
The main difference would be that the security of UBI would give them more power to distch a job if they were being abused in some way, rather than being so desperate that even if their employer is abusing them they are forced to take it because they need the job to survive.
I feel like too much discussion on UBI is poisoned by the idea that the vast majority of people are bone idle and are willing to just sit at home doing nothing and just existing with the bare minumum required to live. It's just not true
No matter how you finance it, you can find other (better or worse) means to spend collected money.
In the name of simplicity, you might want to have a single government agency that assesses your income and net worth. Instead of having both the tax people and the welfare agencies do that and duplicate work.
So instead of having welfare payments phase out, you could just increase marginal income taxes by the same amount, and end up with exactly the same net payment structure.
In euro style systems very few people receive welfare at a given time. Many people may receive it at some point in lifetime, but not at the same time. UBI would completely change the picture.
On top of that, salaries for basic jobs would need to get much higher to incentivize people to work. Thus UBI would have to be much higher as current welfare. Unless you expect citizens to live on UBI but keep services cheap with cheap migrant labor.