Why pay stamp duty on authorized capital when private companies can take loans from directors

This is a question that has always bothered me and which I have never been able to answer (self satisfactorily) for my clients: For a Private Company, when the directors can lend money to the company in the form of Unsecured Loan, why should they pay heavy stamp duty on authorized capital? Why not keep authorized and paid up capital at minimum of Rs. 1 Lacs and bring in money as an Unsecured Loan?
(I am aware of the debt equity ratio being sacrificed which maybe looks bad from a finance point of view for lenders, but this is not a valid answer for cash rich / service based companies that don't want to take loans, and besides, there are ways to get around this as well.)