As most have already noted grenades were not beneficial in open field or line combat which was the method of the day. A grenade is effective to 25m which puts the thrower in danger if they're not able to utilize cover. Grenades are perfect for CQB, and room clearing. Naval combat used them extensively cause of the nature of room clearing onboard a ship. If you stick your face through a hatch to see if it's empty you risk getting your head blown off, so it's better to drop a grenade through it and clear it with violence rather than vision. As warfare evolved into what it is with soldiers utilizing cover, trench warfare and city warfare the use of the grenade excelerated because it's more useful in those environments.