why does the government need to do this?

Because it's important to the welfare of the country itself to have a healthy populace. I'm not saying that there aren't worthless people out there that will continue to be worthless no matter what (some of them are even wealthy anyway), but there are a lot of people who would like to contribute to society but are unable to because they can't get healthy enough or pay rent or whatever. Society would be better if those people were able to be productive. I think it's the government's responsibility to deal with that.