because there not the only ones in the market, apple also offers their over-priced under-performing macs but barly any one buys them, and Linux is usually a second OS on a computer
I don't blame the people for wanting 1 standard in operating systems, that way theres no compatibility issues
sure the wii sells alot but 3rd party games don't sell on it, devs don't develop for it cuz they think its underpowered and its aiming for a totally different type of audience