'Your claim that "way more stuff is running at the same time" is only true if the PC user deliberately decides to keep other programs running alongside their game' - So did you deliberately decide to run virus scanners, Microsoft telemetry, anti-cheat-software, preloaders for browsers like Chrome so they start up faster, explorer plugins and the usual assortment of bloat- and malware? No offense, but thinking that nothing ran on your computer unless you deliberately start it is naive. Why do you think there are so many "PC-Cleaner"-Tools? Even for Android there are "game modes" and "memory cleaners". I have never seen anything similar on a gaming console.

'It is true that while developing for PC you have to take account that different people will have different hardware, but that problem is solved by having a graphics settings menu.' - And what do you think who designs the content that you choose from in that menu? When artists create meshes and textures they have to decide on resolution and polygon count. If your graphics card simply does not have that much memory then the performance is going to drop significantly. So if you want to have the option to lower the graphics settings you need to have assets that require less memory. I mean sure, some engines offer generic settings menus and there are algorithms that lower the memory footprint of assets algorithmically, but if course the result won't be the same as if the assets were manually designed for that size. And if the assets are designed for a lower footprint a slider won't be able to magically add details. The same applies for shaders. If the performance of the hardware is not sufficient a generic settings menus will only switch off effects, and unless you create an alternative the result may look pretty rough.

So that settings menu may be a solution for the players, but for the developers it means that all the options you can choose from need to be developed and tested, and that takes time and money.