Honest question, why phones needs 8GB RAM? I have 4GB iphone everything works well. I have 8GB macbook, things are pretty snappy. Unless you like do 4K video editing...
It is exactly the same phenomenon as we have had since the beginning of a computer era.
The original iPhone, released in 2007, had 128 MB of RAM. But then it was not running iOS 18 either, nor was it using any sort of AI. Of course, you can still browse the internet with this original iPhone, yet your experience of it will be much more limited.
As the user expectations grow, the RAM, etc. all need to follow. The same principle applies to desktop operating systems.