Why do I have to download iOS 7.0.3 on my laptop to restore my iPhone?

I already have iOS 7.0.3 on my iPhone so why do I need to download it to restore my iPhone to it's factory settings?

Added (1). I have the latest version of iTunes

Just the way iTunes works.

The easiest way to update to iOS 7.0.3 is through Over-the-Air updates if you wish you can download it manually & update via iTunes, Full tutorial are given

  • Will I still have my iphone backup if I restore my laptop? I need to restore my laptop because it has a buttload of viruses on it. I'm moving my important documents onto a 500gb flashdrive before I restore it but when it's restored will my iphone remain the same after syncing it or will it lose it's backup?
  • Why won't my new iphone 5 download my music when plugged into my laptop? My old iphone 4 downloaded just fine. Normally I take the music I didn't buy from itunes and just "select all then drag and drop into my iphone folder thing on iTunes" and it would be added and it was easy for me to do this, is this now not working because I have IOS 7? Everytime I try to drag my music into the iphone place like I used to it just won't let me. What do I do?
  • Why won't all of my apps download when i restore iphone from icloud? All of my other stuff downloaded like the pictures, contacts, calendar, email, music etc.except my apps, they all started despairing one by one.
  • Why won't my iPhone 6 download pics to my Dell laptop? Every time I plug my phone in to my laptop it always pulls up "import pictures/videos" well now when I plug my phone in it won't do that anymore. I don't know why. I need to get these videos on my laptop, but i don't know how. My laptop is a pink Dell laptop I think it's windows 7.