Water is sold a la carte where you live? Do you pay for tap water by the gallon?
You're right, it's not sold a la carte. But it is still sold.
And as for food and clothing, do you typically spend $50,000 in one shot on these?
True, but it still costs quite a bit of money, especially over the year.
But notice those are only quibbles over
how much a person needs to spend. A parent is still
required to spend money on his child. If you refused to spend money on food, shelter, and the water bill, would the courts or society deem you a worthy parent?
If you think that medical expenses are too expensive to require a parent to seek it to save the life of his child, then what is the line? How much should a parent spend on his child before we deem the child "too expensive" and the parent can walk away?
And not being able to pay for them is no excuse. If you couldn't pay for it on your own, we expect the parents to ask for charity. The same would apply to obtaining medical services.
Is this sarcastic?
No.
Consider the alternative. A parent knows his child needs surgery to save his life. He can't afford it. So he goes home and lets his child die. End of story.

Wouldn't the parent ask the doctors if there are other options? If the child could get the surgery at a reduced price? If a charity would pay for it?
Admittedly, we wouldn't throw a parent in jail if he didn't seek these options. But what would you think of a parent who didn't?
And why would saying, "God told me not to ask for charity" makes it all better?

God is being used as a "Get Out of Trouble" card, a universal excuse for doing things that we would normally condemn a person for. Hate blacks? God told me to. Hate Muslims? God said I should. Hate Homos? God's going to damn them; I'm just trying to save their souls by firing them.
As if doing any of those things is God's responsibility.

People can believe anything they want in the name of religion. But the line stays with them. When they start making others suffer because of their beliefs, then we need to make them stop.
Because the bottom line is a vast majority of people are wrong in their beliefs. So we can't use them to dictate morality. We need something far more universal.