And hypothetically speaking, say the government is spending $10k/year on assistance to a disabled individual. If you instead give $10k/year to that individual in cash he would not be able to buy the same level of care for the same price on the private market. He'd get massively short changed. Welfare is far more efficient, financially speaking, than handing out cash to people and letting them fend for themselves.
How do you know that? Countries with much worse welfare than the US often have much better prices than the US when it comes to healthcare.
Maybe healthcare prices were allowed to grow so much only because insurance pays for most of it anyway. If that changes, healthcare providers would have to charge more realistic amounts, especially for common procedures like dental checkups and medications like insulin.
That's just income redistribution from the most vulnerable, right wing would love this.