I'm not sure if this is 100% accurate. My ageing N95 has a "Download" link in the applications folder. This allows you to browse and buy apps. I've never done it because most of the Apps in their are naff and the ones that aren't are not worth the £6-10 they cost to me.
Virtous cycle must be formed between size and quality of the audience and variety and quality of the content. Those cycles do not build themselves. That is why Apple's App Store is a success and Nokia's or Handango is not.