Again that is a separate issue from the no undercutting clause. Prohibition of resale is ubiquitous in the software world because for decades the ploy has been to sell you a license, not an actual product.
Of course I’d love that to change but it’s a core precept of how digital ownership works and has worked for most of it’s existence. Steam is not the main force behind that.
Yeah that’s not what they’re preventing. It’s to stop someone with rights to generate keys, i.e. the developer, from generating a lot of Steam keys and then selling them on their own site at a discount, which is basically leeching off of the Steam infrastructure & ecosystem while sidestepping the storefront. Which is fine as long as they don’t undercut.
The EULA for any software you’ve ever paid for is what forbids resale.
2 is false. It only applies to steam keys.
You’re conflating DRM with software licensing. DRM is digital enforcement of license terms. Steam was by no means the first form of DRM, but it is a DRM platform (though there are some DRM-free titles).
I am not too young to remember Steam being a highly controversial topic because it was basically launched as the DRM for Half-Life 2. The backlash against the normalization of DRM led to the creation of Good Old Games, still the premiere DRM-free vendor on the market.
However, software licenses have been in use since the 70s. The practice of selling actual copies of code as opposed to licenses to use the code was already rare by the 90s. If you bought a CD or floppy disks in a store, you were buying a license to use the code on the disks, but you were explicitly denied the rights to resell or copy it, at least for most commercial products. Most people just never read the very long terms of usage.