So when I buy a CD, I can install the software, and then grind the CD into powder, and since what I bought no longer exists, I can stop paying?

Well the software could disable itself when you stop paying. You stop paying for the value, the software stops providing you value.

Could the molecules from the food stop forming parts of my body?

I am not chemist or biologist but I don't think that is possible.

Impossibility is the only reason it can't? It would be totally legal you think?