This title is super weighted, Valve makes it quite clear that users do in fact own a thing, a license for a product on Steam. This is fundamental to games with online DRM.
Allow me a short incoherent essay on my thoughts on the subject.
Public domain is a fascinating concept to me, My view is somewhat US centric, for example, some countries have no legal equivalent of the concept. but I think the idea that we the public can collectively own something is neat. Nothing wrong with copyright, I think copyright is a very important legal structure recognizing the effort to create something. but I also think it somewhat enlightened to say after a given amount of time the public owns this. Or the way the US government says "works created by the US government are for the good of all US citizens and as such are in the public domain". should a person be allowed to say "I made this for the public good and release any claim of ownership over it". sqlite infamously has trouble because some countries are legally unable to recognize a work put in the public domain. But all of nasa's software and papers are available under the same consideration.
A manufactured item is fairly hard to copy and the law on counterfeit goods is correspondingly weak. There is some law there, but it is hard to get it enforced, usually requires a court battle, etc. for example design of garments are infamously impossible to protect, garment manufactures tend to have to lean hard on trademark law to get any protection on design.
But printed works, It is easy to get a perfect copy, and computers are even worse. Trying to make a computer not copy something is like trying to make water that is not wet. This is the domain that copyright law started to appear. Basically laws explicitly saying you own what you wrote and get rights about decisions on when and where it can be copied.
But the point of my rather long-winded and incoherent rant is to say they can and do sell copies. when you buy a work those bits belong to you. you can do whatever you want with them... well, almost whatever you want with them. It is illegal to distribute them to others as this runs afoul of copyright law.
Running software without a license is literally illegal (at least in the US). Now, whether that is enforced, and to what extent in practice is a different story, just like how piracy in general is not really enforced against.
Mere execution and usage of software is simply not something copyright law cares about, which is why your assertion that
> Running software without a license is literally illegal (at least in the US).
is wrong. There is nothing in the law that gives copyright owners an exclusive right to "usage", only to the making of new copies, their distribution, derivative works, public performance, etc.