> Why not build your own hardware

Haven't looked at this in depth, but designing and manufacturing a phone with a similar miniaturization level and performance to commercial models is a huge electronics/firmware/design engineering challenge. Additionally, often the datasheets for processors, etc. are difficult to obtain and/or under NDA.

Nothing a group of determined engineers with the funding and connections couldn't achieve, but it's no easy task. Fairphone required a few million $ to develop the first model.

Either way, developing software is hard enough - having to build hardware too moves the project toward "pipe dream" territory IMO.