It looks you are talking about listed companies first of all.
Though I would request you to tell us the source from which you have come to this conclusion, following are my comments (please correct if my understanding with your question is wrong or not related):
1. When a company comes with an IPO the minimum public shareholding requirement is 25%, however, by following rule 19(2)(b) of SCRR by following certain conditions the public shareholding may be restricted to 10% and the promoters may hold 90%.
2. Now, with the recent circular issued by Ministry of Finance, all the public companies with promoter shareholding more than 75% have to make necessary arrangements to bring the public shareholding to 25% minimum. And the maximum time frame which a company can get in this is 3 years as every company has to disinvest its promoter shareholding by minimum 5% per year.
3. According to the above, whether it is media, infra or any other company, now every company has to have a minimum public shareholding of 25%.
4. Delisting is not the result of bringing promoter shareholding down , in fact, further public offering is the one which all companies would opt for increasing the public shareholding.
Thanks and regards