Why is hdmi 2.1 so important (apart from 4k)?

I have been using the same hdmi cable from ps3 times for 5 years and still get 144 fps on my monitor (or 144 hz) and that's not my imagination you can clearly see the difference between 144 fps and 60 fps

That's why I don't understand why everyone panics because they don't know what kind of hdmi cable to use, for example for the ps5 or xbox

The bandwidth of HDMI 2.1 is extremely high compared to its predecessors in order to transmit 4K @ 120Hz with HDR.

Most of the questions are not about the (cheap) cable but about the required end devices.

Ah okay