Google Drive and iPhone 6

Why can't I install Google Drive on my iphone 6? It was on there at one time but I rarely used it and now it will not install. I have the latest version of IOS, I have logged out and back in to the App Store, iTunes, my Apple account in settings, and I have restarted the phone multiple times. I have also removed a number of apps in an effort to increase storage space. It still will not install.