Probably an unpopular opinion, but I don't think most people who buy a Linux phone actually want a Linux phone. They want an open-source phone. The Linux philosophy isn't important to them, they essentially want open-source iOS (with all of the polish and out-of-the-box doodads). They want the ability to make modifications, and they want the freedom and transparency that open-source gives them, but they don't necessarily want to open a PR against the camera app if they want it to more closely match the polish of iOS.

That was my first thought. What does a linux phone offer a user (feature/usage-wise!) that my jailbroken iphone didn't?

...back when I felt the need to jailbreak at least - now with altstore, ios improvements, or my own dev-ish - I am good.

It allows me to run any linux desktop program, which includes programs that can be run with wine, anbox or even a virtual machine. If it's fast enough i wouldn't need a PC at all.

So I would say that is the long term goal: convergence. Linux has a major advantage over other operating systems in this regard.

wine alone wouldn't allow you to run x86 apps

edit: Hangover lets you run x86 programs via Wine on ARM platforms: https://github.com/AndreRH/hangover