One of the problems with this is that a large number of those claiming universal credit are in work, and the benefit acts as a subsidy for employers who don't have to pay their employees enough to actually get by.

It also doesn't affect PIP, which is not means tested. The only way to reduce PIP claimants without harming disabled people is to fix the absolutely humongous issues with the NHS that are leaving more people without treatment or even a diagnosis for far longer than it should.