I can not answer for the other guys. They probably have their reasons.
As for me, I made AiPC for a couple of reasons. Having the winblows desktop on a car just does not seem right. It does not look like it belong there. So I created AiPC for my personal use but I shared it with the rest of the pople.
Also, my interface seems like it came out of the factory. It looks one with the car and it looks pretty nice IMO. At the end of the day, you are limited to what I put on the software but it looks more professional.
Also, I am not sure about the rest but AiPC was created with "me" as the main user so it's prefect for me. There are things with ME that I am not too found of and I refuse to pay 25 bucks to Gnet. Now I have a software that is better than GNet (using the same program to creat it) and it's free!