Apple is making luxury goods, they're not going to drop their prices.
It's like how there's recently been a bunch of articles about how phones are getting "too much" RAM and the comparison is laptops.
When the question should really be, why do laptop manufacturers get away with putting 4 or 8gb of RAM in a laptop and mobile phones are catching up.
And anyway. What most people do is use their devices however they want with the expectation that everything runs smooth, they can multitask and the demands of higher quality video/pictures/refresh rates can be met.
Of course there are people that are satisfied with yesterday's technology. Plenty of people use 10 year old ThinkPads and get their work and entertainment done. Same with getting a £100 smart phone.
I think this is comparing cheap laptops to expensive phones.
Meanwhile, my very high-end gaming PC struggles to play the video files from my iPhone at 60fps for some mysterious reason.
H.265 support in graphics cards and consumer processors has laughably lacked behind on mobile, probably because of licensing.
There's also the fact that a lot of video applications on Windows don't enable hardware decoding by default out of fear of encountering buggy drivers or hardware.
On mobile there's basically only one way to decode video, which makes use of all the phone's dedicated hardware, while on desktop applications can use a wide variety of codecs. Then comes the decision whether to decode on the CPU or GPU, as both have hardware decoding support these days, or to fall back to software decoding because the specific combination of codec and bit depth wasn't supported by the hardware of choice.
Then there's the fact that Apple logically encodes video the camera records into a format that iMovie is well optimised for. If you encode video with your PC's GPU, it'll probably be just as snappy playing back while the iPhone video might still be struggling.