Web based or PC based trading?

I was wondering over the weekend about the reason why there aren’t that many really good web based trading platforms. All the great trading platofrms seem to be PC desktop based.

The technology for developing web based systems have evolved to a point where you can almost do anyhting you can do in a normal PC desktop based application, yet no one seems to be writing something to run web based only. Am I missing something?

Looking forward to your views.

Thanks,
John