7 Edge isn't mathematically optimal because humans are either wasting points or short points on Magic because of how the Priority table is set up.
6 Edge you don't wind up with very often either. A Mundane would need 5 Adjustment points, which isn't an option on the Priority table. An Awakened character would probably want 10 (or more) Adjustment Points, so you'd need to be non-human and put in a B to Metatype.
5 Edge will happen to a lot of Mundane characters, especially Humans. E Magic ('cause Mundane) and D Metatype for 4 Adjustment points...just going to work out that way a lot.
If you could get a 6 or 7 Edge from the Priority table naturally, I'd agree with Smogg. 7 Edge on a combat character gets lulzy. But in practice, a 6 or 7 Edge is a significant build goal that will require some (IMO anyway) potentially sub-optimal choices.
Mind you I totally have a theory crafted, Way of the Burnout, Stolen Goods, Physical Adept Gunslinger that does a 4 Edge Boost (Anticipate or Add Edge), for 3 consecutive Major actions, skips a beat, and then has a fourth 4 Edge Boost ready to go on Turn 3 if needed. But it gives up either Skills or Resources for that trick compared to the same build with 5 Edge, that (when it all clicks) still gets 3 out of 4 Major actions on the first two turns with a 4 Edge Boost. And seriously, if that doesn't clear the map, you're probably doomed anyway.
So 6 or 7 Edge isn't, per se, inefficient. However, the way the Priority table actually falls, makes it something of a compromise for many builds. Awakened Metahumans with an E resources are the primary exception I can see.