Which implicitly means: "everyone must always pay into the government pool."

If low-risk individuals are allowed to make their own choices, they will choose an insurer that caters to their group, thus depriving the government "option" of "premiums."

Just like with school property tax vouchers: if people are allowed to directly appropriate the benefits of their funds, less "desirable" schools would receive less funding.

Mandated government "insurance" is a form of welfare.