Less reliable, heavier and harder to use and less immediately effective than more recent designs. Grenadiers were a dedicated unit in some cases just to section off the dudes that were big enough to throw it out of range of their own people, much less carry them around.

They did have some use cases, particularly times when you could drop them into a hatch or strong door instead of having to hurl them yourself, they just weren't widespread like the 20th century.