See, that's the thing: I as well think that there is no need for folders on the start screen... but nobody is talking about that... at least I wasn't.
I want folders for the applist. You're right of course when you say "you can just swipe to the right and see a list of all your apps and just tap the letter heading and select the letter the app starts with, and go right to it". That only works, if your organizer APP is named "Organizer", the dropbox App is called "Dropbox", the epub reader app is called "Epub Reader App" and so on... There are quite a few Apps which have names not related to their tasks. The "worst" ones are third party apps like "BoxShot Free", which is a Dropbox App. So for doing what you mentioned in your sentence, I have to know what the name of the app is to search for it, right? If you don't remember the App, you are forced to check all the apps until you find it...
This might be a smaller problem for folks using just 20 Apps or so... But for people who have mor than 50 or 60, there is quite a chance to forget the names for a second (Apps one uses twice a month are terrible for this^^)..
And the other thing is: task related folders! As I mentioned before: I use foto manipulating apps sometimes and have 7 of them on my phone. But because of the different names, they are all mixed up and not together. A lot of times I change the apps a few times during the editing proces. It's really annoying to search for them all the time...I could pin all of them on my Screen, yes... but that's not the point. I don't need them all the time, so that would not make sence...
But all in all:
That's not a huge problem for me. So I don't really "need" folders all the day. But what I don't like is when people try to "explain" to others how stupid it is to use folders, because that's so lame and old...bla bla bla... If someone thinks he needs them, just let him...