> Any good argument that anyone can think of for a scenario where smart eyewear will not be as ubiquitous as smart phones eventually?

I see 2 potential scenarios:

1. Some series of safety/privacy mishaps will lead to social/media hysteria which will push politicians towards a ban for such devices.

2. Initial price set too high will cause vicious circle of: low userbase -> lack of interest from developers -> lack of valuable features -> low userbase.

I won't argue that these are very probable scenarios, but quite possible imho.