This year, no. If 50% of my income is taken as taxes, but I get $30K of it back, I'm still doing great. But my sister and her boyfriend would - $30K is more than they each make right now, there'd be no reason at all for them to work. They'd actually come out ahead, since they're not excluded from taxes. They'd end up with a higher effective income than they currently get. The same is true for... about a third of the people in the US. So let's assume that 50% of those are kids or retirees who aren't being taxes anyway... and you still end up with about 15% of the US workforce being better off not working at all than they are now.
Well sure, you might say... but wouldn't they want to continue working and get $35K instead of $30K? You're assuming that the desire to have a slightly better standard of living is more influential than the desire to not work at all and have 100% leisure time.
So a chunk of people are going to stop working. And that means that in year 2, it's not 50% of my income, but 55% of my income that is taken as taxes. Then it's 60%, then 70%, then 80%. My standard of living reduces with every tax increase, because my effective income gets smaller and smaller. At some point, you're asking me if I would be willing to work at my same job - which has a high degree of responsibility, accountability, and effort involved - so I can have $10K of after-tax salary plus $30K of free money? Nah. I wouldn't. At that point... probably a lot sooner than that... I can quit my job, move to the middle of nowhere and get a goat or two, take up painting, and long walks, and not have to do anything at all.