>>724699278 (OP)
Because rather than having a person make assets for the 242FPS and making sure it looks good in motion, you're expecting a computer to automatically generate 8x the number of assets on the fly and cram them in there with some algorithm which will probably not look very good. It'll come off as jerky to stilted or blurry as a result. This is also an excessive extra workload on the PC, since to go from 28FPS to 242FPS means generating 8 upscaled frames for every 1 actual frames and the computer is the one that needs to generate all that extra rendering on the fly. Upscaling from 720p to 4K is much the same problem, blurring details or adding incorrect ones by necessity.
The only excuse for NOT putting in the work is because the company wants to save money by not paying labor. So it's a company deliberately making a cheap and lazy profit in the hopes that the user's CPU can pick up the slack. I'm not giving a company $100+tip when over half the game is being generated on my own GPU and they didn't do any of the work.