Does Steam let you control the whole dependency tree of your software, including modifying any part of it and rebuilding from source as necessary, or pushing it to a whole other machine?
Real life software is much more than just downloading a game and running it.
Pushing to another machine? Yes. By strict definition. Steam exists to sell pre-compiled proprietary programs for dollars.
Rebuilding? No. Linux package management is so-so at allowing you to compile programs. But they’re dogshit garbage at helping you reliably run that program. Docker exists because Linux can’t run software.
> Real life software is much more than just downloading a game and running it.
Real life software outside of Linux is pretty much just downloading and running it. Only in Linux we don't have a single stable OS ABI, forcing us to find the correct package for our specific distro, or to package the software ourselves.