Consider this question: why is it moral to own property? Why can you possess something you don't use or need, but can prevent me from taking it, or using it?
That's an excellent question. But it raises another: is there a workable alternative? Can society function with no concept of personal property? Examining that question might help to answer the first question: 'why is it moral to own property?'
I'm listening. Can society function with no concept of personal property? What conditions would have to exist where everyone could have whatever was needed, without denying anything to another person?
The only thing I can imagine is a very dreary environment where there would be enough food and water for sustenance, but very little variety. We would of course be naked, so I hope the nights are cool and there is plenty of shade.