Please note that there is no legally binding clause that Civ 5 work after you installed it.
(...)
If the game doesn't work on your computer for whatever reason, you're typically (censored). Even more now, since more and more games come with one-time activation codes, and stores are learning not to take back games that "I couldn't install".
As already mentioned in the paragraphs before my question, that was not my point. If a company correctly noted the technical requirements for the game on the box (which they are required to do), then it's entirely under my control whether I can play the game 15 years from now or not. I can boot into multiple versions of Windows, I have a second computer and a storage of old spare parts, and I'm quite confident that I'm technically literate enough to give every old game the environment it needs. For example, I have no problem running the original Daggerfall on my secondary computer - it took a while and I needed to change some parts, but it worked. I currently have several hundred PC games in my collection and I assure you that each of them still works, because for each of them this matter is entirely under my control.
Steam now takes this control away from me. With Steam, I can
not be certain that it is under
my control whether the game I purchased keeps being playable, because Steam explicitly keeps this control for itself. Steam actually explicitly states in their license that they can terminate my license whenever it pleases them and, should I disagree with their reasoning, my only option is to leave earlier (and I could try to sue for a refund, which still wouldn't give me the purchased products back).
That's because no company will commit itself to a legally binding clause for circumstances that are not under their control. That include committing itself to actions in case of bankruptcy - placing an undue legal burden on any buyer is a sure way of making sure no investor will touch your company with a 10-foot pole, even before bankruptcy
Well, that's a common argument, but considering the rest of Steam's argumentation it doesn't really make sense. When people are asking "Will we be able to play our games even after Steam is gone?", then Steam says that there is a system in place that can remove the DRM under these circumstances, the system is already developed, tested, confirmed working, and they'd "presumably" use it in such a situation. So it all sounds very easy. However, as soon as someone asks "Then why don't you guarantee it?", the whole construct which was so easy and devoid of any problems before suddenly becomes a "poison pill" which would deter investors.
You see the problem of Steam's (and your) argumentation? Either there actually is a DRM-removal system in place and the really do intend to use it (and their contracts with their business partners allow them to), in that case there's no risk of putting it into the warranty. Or there's a good chance that said system cannot be used (due to considerations of fromer or future business partners, investors, etc., or due to the system not working in the first place), then they of course shouldn't put such a clause into their license, but they also should actually inform their customers of these risks instead of trying to give them the impression that there's absolutely nothing to worry about.
So, no. There is no legal binding "we will support you in perpetuity", there never was, and there never will be.
The day when a "required repeated authorization to actually let you play the game you paid good money for" is labeled as "support", will probably be the day when I limit my further collection to indie and Open Source games.
I'm not asking for "perpetual support". I'm asking for reliable security that they don't suddenly take the products I purchased away from me for whatever business reason might sound convincing to them in the future. I have this security with all of the several hundred games I own. So far, I don't have it with Steam, they explicitly exclude it in their license. They justify their DRM system with the necessary battle against piracy, but in fact they are taking rights and control away from their legal customers.