I'm pretty sure that when it comes to apps linked to a well known brand (e.g. Picasa, Twitter, Flickr) or solve some kind of specific problem (todo, email, finances) do have downloads primarily from search.
Discovery by being promoted or top ranked only works for apps where downloads are impulse-driven, games being the primary example. Searches on the other hand are intent driven, initiated by users that want to get something done. And I don't think developers of such utility apps want massive downloads, they just want to make a profit.
Also your argument about discovery needing top ranking is circular. To get top ranking you first need discovery. This is where iTunes fails its customers - as it focuses on the new and the shinny, creating an environment where apps that build a reputation slowly have no place, which is why most apps in the app store are released in a fire and forget fashion.
Discovery by being promoted or top ranked only works for apps where downloads are impulse-driven, games being the primary example. Searches on the other hand are intent driven, initiated by users that want to get something done. And I don't think developers of such utility apps want massive downloads, they just want to make a profit.
Also your argument about discovery needing top ranking is circular. To get top ranking you first need discovery. This is where iTunes fails its customers - as it focuses on the new and the shinny, creating an environment where apps that build a reputation slowly have no place, which is why most apps in the app store are released in a fire and forget fashion.