Coming from outside the App Store, two things always stick out at me:
1) They have totally nailed the purchasing experience. I think that probably increases sales system-wide by well in excess of a factor of ten, and it powers factor #2.
2) The use of iPhones is social in nature. Not fake social, like Facebook apps. Real social: hey, look, my cool phone can fart. Folks I know with iPhones pull them out at dinner and show me how much fun they're having slinging birds around. And darn it, I want to sling birds, too. That is why Apple loves the apps: because each one is a recurring opportunity for you to explain to your friends "Here's what you could do on your iPhone, if you were cool, but you can't do it because your phone is lame", why Apple is trying its darndest to kill cross-platform development ("Big deal, I have that game on my Droid"), and why some developers are sort of falling into accidental virality through quality of experience. (Some others, of course, are intentionally engineering the virality.)
I mean that use of them is about as solitary as games get, and the prevailing reason they're known as "social" is because of artificially engineered spam-your-friends-to-advance mechanics. I play a particular RPG on Facebook -- beating some monsters requires getting 100+ folks to click on a viral link for you. We've got our own little social norms and lingo for dealing with that: I click on your link and tell you "PRTF http://example.com/12345 -- for "please return the favor", because since I'm telling that to several dozen people I don't know and don't care about every day I'll be darned if I actually type it out.
None of my friends have ever come over in real life and told me "Patrick Patrick guess what guess what I got a new FarmVille cow." That would be really, truly social for me. (And I say this as somebody who regularly hears stories about WoW loot or D&D games from days gone by.)
To keep with the anecdotes - I have friends who when they meet up normally pull their laptops out for some farmville (and to plan how to get the next level/cow/whatever). It does happen.
But great observation on the iPhone games thing - one of the discussions at our extended family dinner every couple of weeks is the new iPhone/iTouch apps we have.. "Hey check this out" is really effective marketing (as of course it is in every industry)
1) They have totally nailed the purchasing experience. I think that probably increases sales system-wide by well in excess of a factor of ten, and it powers factor #2.
2) The use of iPhones is social in nature. Not fake social, like Facebook apps. Real social: hey, look, my cool phone can fart. Folks I know with iPhones pull them out at dinner and show me how much fun they're having slinging birds around. And darn it, I want to sling birds, too. That is why Apple loves the apps: because each one is a recurring opportunity for you to explain to your friends "Here's what you could do on your iPhone, if you were cool, but you can't do it because your phone is lame", why Apple is trying its darndest to kill cross-platform development ("Big deal, I have that game on my Droid"), and why some developers are sort of falling into accidental virality through quality of experience. (Some others, of course, are intentionally engineering the virality.)