I bought my first iPhone in 2008 primarily because it gave me access to live bus arrival times and an interactive map. Other reasons that were far less important were the ability to look up random stuff on the internet, the fact that I hated the UI on my dumb phone, and the fact that I was carrying an iPod anyway so one device was more convenient than two. The main drivers addressed a real problem -- finding my way around when I don't have a computer nearby.
I have a feeling you may be right in the long term that Glass may prove successful, but I just don't see anything like the same benefits. My smart phone gave me fundamentally new capabilities. Glass seems to just make them more convenient.