If it's wrong to use it on a tube of toothpaste because that's stealing, then it must surely be right to instead buy the maximum food and throw it away. Therefore, people should do that.
If that sounds wrong to you, then the initial assumption might not be correct. Maybe it's not so bad to buy the tube of toothpaste.
Constraining yourself to extremely hard and fast rules seems like a good idea on the surface. But it's all about incentives. I can easily make the company bleed much more money while being within their rules. So why even bother?
A touch of leniency and common sense goes a long way.