Health care is a limited resource, currently allocated by price.

Under the new legislation it wont become any less limited, but the allocation mechanism will change. The change may affect the overall availability of health care, but that is a feature, not a bug, for some people.

Part of an essay by Thomas Sowell may help to explain the motivation:

Liberals have never ceased denouncing Ronald Reagan’s “tax cuts for the rich” in the early 1980’s, despite the actual results, including a record-breaking period of economic expansion.

After the tax rate was cut on the highest income brackets (and on other), not only did the total tax receipts rise but the percentage of those receipts paid by “the rich” also rose. Why then were the liberals unhappy? Because those in the upper brackets paid these vastly greater taxes out of rising incomes, while retaining a higher percentage of those incomes for themselves.

The dog-in-the-manger principle requires that the rich be made worse off. Any policy that fails to do that has failed politically, regardless of what economic benefits it may bring to the society as a whole.

From “Dog-in-the-manger Politics”, Thomas Sowell