Whether you get the sandwich from an owner or not cannot directly affect anything but the amount of money you have afterwards. But if a program has an owner, this very much affects what it is, and what you can do with a copy if you buy one. The difference is not just a matter of money. And it causes intangible ethical pollution that affects us all. But what software owners typically deliver is a black box that we can't study or change.
Society also needs freedom.
When a program has an owner, the users lose freedom to control part of their own lives. And above all society needs to encourage the spirit of voluntary cooperation in its citizens. This is why we say that free software is a matter of freedom, not price. The economic argument for owners is erroneous, but the economic issue is real. For ten years now, free software developers have tried various methods of finding funds, with some success.