Why isn't iOS7 compatible with iPod 4th generation?

iPod 4th generation is a fairly new version of the iPod and I just got this like 2 years ago. I don't want to get a new iPod just so I can get iOS7, that is pointless. I think that the Apple manufactuers should change iOS7 so that I can get it on my iPod 4th gen. I'm mainly posting this hoping that someone who can change iOS7 sees it and does something..... 😀