Like I said, industrial environments. A small niche group of people and businesses who could use some information in front of their face as they do hands-on work.

Estimates of the size of this market were in the single digit billions of dollars for Google, who bailed out of Google Glass recently: https://www.cnbc.com/2017/07/18/google-glass-enterprise-mark...

For comparison, the iPhone makes $200 billion in revenue every year. Apple Services (Music, TV+, etc) make something like $20 billion every quarter.

Apple does not enter many businesses that only have the potential to make $1-2 billion.