Mobile challenge

I read an interesting observation is Vihaan's brochure that went-

Why does mobile have only 20% market share of phone calls, even though penetration is above 90% ?

I think this question emphasises the market opportunity and the challenge for a mobile operator. Of course, there are solutions in the market that can be used to tap the opportunity. Lets look at them-

1. Mobile operator deploys micro/nano/pico cells within enterprise premises. Enterprises get a private numbering plan, pricing scheme.
2. Mobile operator deploys mobile PBX that runs on the operators network and offers enterprise grade telephony features.
3. Mobile operators enter into a definitive agreement to handoff traffic to private wireless in-building networks

Each of these solutions have opportunities and threats associated with them. At this point in time, I am hearing of the use of option 1 at most.