I dove into the Wikipedia article about handgrenades. There's a common separation between offensive and defensive grenades. Those which cause shrapnel are usually considered defensive grenades as they're having a larger, unforseeable area of effect and because of that you want to throw it from a defensive, covered position. But often times offensive grenades which usually cause harm only through their shockwave could easily be upgraded with a metal cover that will provide a shrapnel effect.