Which is heavy on the CPU and GPU...

You don't know much about encoding or decoding either.

It's called decoding and encoding.

But the big data centers doing all the video processing for the big video services (including both permanent videos from a library and things like live streaming) are encoding the videos with settings that require less computational power to decode. The idea is to be able to let even old budget smartphones still be able to display the video with very low power requirements on the client device. There's no universe where consumers decoding digital video will be a high-power computational task.

Restaurants have sharp knives in the kitchen, but generally serve food that requires only minimal cutting effort from the table knives set out with the rest of the table settings. Dining will always be easier than cooking, by a margin that makes the difficulty of dining not worth mentioning, so it would be bizarre to criticize a knife as being only good for cooking and eating food, when plenty of dining tableware knives out there would be insufficient for kitchen work.

You've made the mistake of lumping decoding and encoding together based on the algorithmic/mathematical similarity of those tasks, when everyone else is more inclined to discuss the very different end user use cases of those computing needs.