I got few various responses from other investors to whom I had asked this question and I am getting mixed responses.
There are few brokers / depositories who dont charge for debiting script from broker pool a/c.
I have an a/c with RKSV and they charge Rs 22 for every script debit from pool a/c. so I think low brokerage charges are being set off against high demat charges for investors who hold shares for short time in delivery.