I've had a pair for the last 6 months. Honestly at this price point ($1500), you must really be a geek to be willing to buy one. IMHO it's not ready for rollout. The limited voice UI and the battery life make it useless for actual consumer usage.
Nobody automatically knows why they need most products. That's why even Apple's advertising is built around demonstrating use cases for products like iPad and iPhone.
Marketing for Glass probably shouldn't try to sell Glass itself, they are trying to sell the use cases and lifestyle that it enables.
Sorry, I already have a Go Pro ($250). That is basically the end-user for Glass ($1500). But keep at it Google. Glass will make for a platform for interesting further UI and wearable experiments.