The simple reason for booking closure for public is that fleet buyers from Government sectors, armed forces, institutions and business groups get priority in furnishing orders. Following that are the greedy dealers who have developed a sense to earn 'ON / hoarding premium by themselves by booking extra units under their associates' names and calling then 'investor ki gari'.
All these numbers combined together are way more than the real private consumers at any given time. What Indus will sell to these bulk customers in first year of launch will probably be in equal proportions to what its going to sell to private citizens in the coming few years so when someone quotes them saying, 'they are not under any pressure or obligation to produce more, reduce price or upgrade' they are right.
And moreover there are always a pinch of customers who are willing to buy anything new no matter how impractical or expensive it may be...may it be CH-R or X1 or Vitara @ 4mil.