Because for many (maybe even most) people, amphetamine and methamphetamine are the most effective focus enhancing drug known to man. Meth has a crazy stigma attached to it though, so most people looking for enhancement prefer the pharmaceutical pills.I'm pretty sure amphetamine is a controlled substance (or the equivalent) in India as well... meaning you need a license, and if you have a license, it's probably more profitable to sell to reputable licensed pharmacies that require prescriptions. Where there's licensing, there's usually oversight, and oversight can mean it's more profitable to follow the rules -- which would leave very little being sold to unlicensed parties./end pure speculation