Let's put ourselves in the shoes of the regulator SEBI for a change. One of the main reasons why they must've considered to limit retail traders' participation in derivative could be because of traditional brokers' malpractices! As most of you know, many traditional brokers' dealers & sub-brokers place derivative trades in clients' accounts with and without their permission which often causes HUGE losses in the clients' accounts in a very short span of time. The clients who are usually very gung-ho based on the broker's promise at first become shocked at the quantum of losses and some of them file complaints against the brokers to the exchanges' Investor Grievance cell or SEBI. Over a period of time, the complaints have accumulated causing worry to the regulator because each time the broker promises to never repeat such practices but it is beyond their control because the structure of their organization is designed to trade/advise on the clients' behalves. In the last few years, SEBI has tightened the screws on unauthorized trading and has introduced compulsory call recording etc. Recently, there has been talk of introducing penalties if anyone is caught indulging in such practices. As a regulator, they're trying to ensure that retail traders' are less susceptible to risk because of old-school greedy brokers. Since, they cannot come and check every phone call or trade, they want o resort to such measures.
This is obviously not the only reason, but they may have definitely considered investor complaints while forming a conclusion. This is my educated guess. There needs to be more research on how many trades are executed by clients on their own behalf and how many are executed by brokers in comparison. In my opinion, the penalties for unauthorized trading should be levied with an iron fist by SEBI to weed out the bad apples once and for all. The larger majority of the sub-broking community is not as straightforward and malpractices maybe more rampant than we might assume on this forum. However, I disagree with their solution of wanting to restrict retail traders in F&O. Such a solution will create problems rather than solving them.