MTF trading on Zerodha, and exclusive cash margin criteria.

I have seen a new trading option MTF getting introduced on Zerodha; some other brokers have named it "Buy Now Pay Later". I went to SEBI guidelines, NSE faqs, and ICICI direct blog on it which are mentioned below [https://www.icicidirect.com/research/equity/finace/sebi-eases-cash-collateral-rules-for-mtf](https://www.icicidirect.com/research/equity/finace/sebi-eases-cash-collateral-rules-for-mtf), [https://www.nseindia.com/trade/members-faqs-margin-trading-facility](https://www.nseindia.com/trade/members-faqs-margin-trading-facility), and [https://www.cse-india.com/upload/upload/Nov\_3020221.pdf](https://www.cse-india.com/upload/upload/Nov_3020221.pdf) They all say that initial margin and maintenance margin can be paid as cash, cash equivalent, or Group I equity shares or units of Group I Equity ETFs (obviously all the cost incured like brokrage and other charges including loss must be paid in cash). The main benefits of using MTF are to get low interest rate and freedom to trade low volumes (if half or more margin are available in account). However, Zerodha wants it all in the form of cash in their account on which they provide negligible interest. Moreover, their interest rate for shortfall (the loan are mandatorily given by Zerodha) is 15.72% annually (more than 2X risk-free return and equal to personal loan interest rate). This interest is too high since it is provided over collateral pledged after buying and I think more secure than home loans. Stocks have volatility, but zerodha has done their risk assesment and allow MTF on chosen stocks only. In Future contracts people can get interest rate of 7.5% annually and they can short sell as well where they receive interests in form of higher selling price (MTF do not allow short selling). My question is why Zerdodha is introducing such predatory practices. What will be the best broker to trade MTF on? Who are the people who are paying 16% interest rate, pledging charge, and brokrages, and are still profitable?