Did google try to release chrome for ios and get blocked by Apple and I didn't hear about it? There are a ton of third party web browsers for ios.
There is big board hanging on the door saying its not allowed. Why would any company spend resources on projects that can't be shipped. All the third party browsers currently in app store are either skins on safari or interprets stuff on server side like opera mini.
In other words there is only one true browser allowed on ios - Safari.