I have a iphone 4 why can't I update to IOS 8?

I have a iphone 4 why can't I update to IOS 8? - 1

Unfortunately iOS 7.1.2 is the latest it'll update to. Older iphones aren't designed to run these newer OS's. Plus, I'm pretty sure Apple would make less money if older iPhones like the 4, kept being updated.

IPhone 4 can only go up to 7.1.2, if you want IOS 8 then you will need an iPhone 4S or newer.

Its outdated.
You know just how slow it gets with iOS 7. IOS 8 wouldn't make it any faster; it may be just the opposite.

Only solution is to buy at least an iPhone 4S or newer.

IPhone 4 doesn't support iOS 8

Like the others have stated, your iPhone 4 doesn't support IOS 8, it is simply too old of a phone. Sorry.