You make a good point but I'd like to think of it this way: If the said service is made mandatory, then it has a chance of succeeding. Else, building that critical mass entails a lot of customer acquisition costs that a Govt may just not be in a state to justify. And therein lies the beauty and danger of network effects. Once a company has them, it is very very difficult to dislodge it. Look at Visa and Mastercard: V has been around since 1958 and MC from 1966. Both are valuable as they have network effects.