Let me ask you this.
Why should I as a phone buyer get the iPhone 8 for 700 when I can get the iPhone 7 for 550? Serious question it seems all the 8 has is wireless charging a faster processor. As for the processor, I don't think that matters as much in 2017 as it used too.
Yes the glass back is cool looking, but many of us put cases on the phone, especially if the back is slippery
It also has a better camera with AR capability IIRC. if you want to play ar games, the upgrade is necessary.