Because being able to carry around a huge screen is fantastic. Being able to play games or use apps with a split-screen layout when I am sitting on the train is amazing. Folding allows it to fit nicely in your pocket and not be too awkward for quick usages such as responding to a message or paying with your phone.

It seems clear to me that all else being equal having a twice as large screen is a major upside. So it is really just a question of when the downsides (such as price, thickness and durability) shrink enough to tip the scales in favour of folding displays.

I was initially sceptical at first but after a few days you really start to appreciate it. A bigger screen is just better for a lot of things - reading, web browsing, video, gaming etc. I put a quadlock universal mount on the back of my case and then I connect it to a quadlock selfie stick alongside a foldable keyboard and a Swiftpoint ProPoint mouse and it means I essentially have a full computing set up that's both portable and ergonomic that can fit in a cross body bag or even a large bumbag. It's perfect for writing but you can even take it further and use it with codespaces on GitHub to code with it. Or if you're into gaming you can get something like the razer kishi, nacom mg-x etc and then you essentially have something similar to the steam deck. I can't see myself going back to regular slab phones in the future. You do have to be careful with it though and it's also highly recommended to fork out for Samsung Care or whatever the Google equivalent is as the screens do have a fairly high failure rate according to the various subreddits.