Why did lot sizes for index F&O change?

The NSE revises lot sizes of Futures & Options contracts primarily to keep the contract value within a standard range, to keep the contracts affordable and standardized. Since derivatives are leveraged instruments, traders do not have to pay the full value of the contract upfront, but the lot size determines their exposure and the margin required. The NSE undertakes lot size revisions to ensure market efficiency and liquidity, and to contracts more acceptable for a broader set of market participants