I put a stereo in my STi. Most of the time the OEM radios are overpriced and the quality is just a little under par. In my case I wanted an MP3 player and Subaru doesn't offer that option.
The only valid reasons I can come up with for not owning the STi is, It has a stiff ride, a lot of road noise and the insurance is expensive. But, all these factors tie into factor that it is a sports car. And when you drive it, you know without a doubt that it's a sports car! BlueSTi "Scary-Fast"