Fidelity is always going to have diminishing returns. Perhaps there's something fishy going on in the video card business, I don't know that, but as someone who works in CGI, the evolution we see year after year makes sense, it's not like there's a hidden untapped potential

I'm not sure if it's such a direct conspiracy, but I'm sure some of this happens inadvertently at least. Developers of big budget games are likely going to target higher end hardware, and API usage that might cause problems on lower end hardware probably sneaks in as a result of that. I'm sure there's some deals between game studios and Nvidia / AMD to get the latest GPUs for workstations at some discount, which probably means the machines they're using for the bulk of development are beefier than the average consumer's (you also probably want a bit of headroom while developing)... But this kind of stuff can naturally lead to higher requirements for software because you don't run into performance issues unless you're very serious about testing on lower end hardware... Which you might care about to some extent, but it's an additional cost that can take away from other aspects of the game, which might make it less marketable (graphics are a big deal for marketing, for example).

Obviously it's not great if a game uses API calls inefficiently and that means it runs worse than it would otherwise... But I'm not really that surprised when it happens? Working on big projects on deadlines there's often a "try the obvious solution, worry later if it's too slow" mentality, and I'm not sure you need any more of a conspiracy than that to account for stuff like this.