It also creates perverse intensives to not work, since hard work is punished, while sloth is rewarded, thus lowering the overall wealth of society.
Also if you take this utilitarian argument for redistribution of income to its logical conclusion, we get socialism where everyone is forced to have equal wealth. After all, if poor people get more utility from extra income than rich people, then utility will not be maximized until all income is distributed perfectly equally. This does not only apply to the very poor in cases of access to food or health care. It can just as easily be argued that a poor person who doesn't have a computer will benefit more from say a new computer than a rich person who already has access to many technological and educational resources.
Socialism would a good idea if the overall wealth of society could remain constant or increase. Unfortunately, high government intervention is always inefficient and lowers productivity, and as you said incentives against hard work are a problem, actual socialism will be contrary to providing maximum utility.
If you push much beyond basic welfare, you start to harm utility by reducing the overall pool of wealth for things that aren't absolutely necessary, you'll begin to have the government providing things people may have otherwise gone out and worked for, harming job creation and the ability for people to choose to go out and work for things etc... vicious cycle.
I think there's a balance to be achieved between allowing the government to guarantee basic health, and only introducing a bare minimum of government intervention and disincentives to productivity. Tricky in practice.