With intellectual property there is at least (by default) a direct link between the work necessary to create an item and its ownership. With physical items the initial ownership is necessarily predicated on having controlled a means of production.
I can create an IP and I do not need to spend hundreds of thousands or millions of dollars to do so. But I cannot create a substantial physical item without paying the people who own the materials and the factories for the privilege of doing so. Why is previous ownership such a critical factor in ownership of new items, separate from the work to create them?
Intellectual property laws have their own issues but at least with regard to them conceptually, intellectual property is more “pure” than physical property.