I'm curious why - they come from Apple in the same 100% clean install-state. Apple isn't like many PC makers, loading the system down with lots of extra software...
I agree that Apple doesn't add lots of extra software, but there is a difference in doing an internet recovery "clean install" on a new machine.
For instance, my rMB came with Pages, Numbers, Keynote plus iMovie & Garageband, even the legacy iPhoto. Upon finally getting it set up, and updating to 10.10.3 (gaining Photos), I still had iPhoto lurking around too.
After installing a few more programs and coming to the conclusion I didn't want them after all, I decided yesterday to perform an Internet Recovery "clean install" on my 2 day old rMB, and it was worth it.
I now have a virgin 10.10.3 install, not a layered update. Also, to keep the downloaded content light weight, the internet recovery install does not include Pages, Numbers, Keynote, iMovie, Garageband, or iPhoto. Just Photos natively. This is a 5+ GB savings of software I won't use.
Sure, I could just remove those apps, but then you'll leave behind library p-lists, caches, etc, and have a painful manual uninstall process to deal with.
I guess my point in that ramble, is that some of the more OCD of us prefer the internet recovery clean install as it is a slightly different build and more lightweight.