From what I remember from the pile of books I own but am too lazy to correctly source; (Von Mellenthin's Panzer Battles, and The Battle for Europe)

The Germans started using the M24 grenade around 1915 during WW1, the main advantages of the M24 was that it could be thrown much farther and therefore from a safe distance, also because of the longer stem when they lobbed it, it had far better accuracy making it ideal for throwing into trenches. Also when the grenade landed, it was far more likely for an M24 to detonate where it landed, rather than rolling around or away from a target before detonation. Also with the stick design it make it nearly impossible for someone to throw it back, because the process took about 1-2.5 seconds longer than with a more apple shaped grenade.

And heres something I just pulled off wiki which kind of reiterates some of what I've said.

"The stick provided a lever, significantly improving the throwing distance. The Model 24 could be thrown approximately 30 yards (27 m) to 40 yards (37 m), whereas the British Mills bomb could only be thrown about 15 yards (14 m)[2] (however the British War Office report "WO 291/472 Performance and handling of HE grenades" gives an average figure for a standing throw of a Mills bomb as 30 yards (27 m), when crouched 25 yards (23 m) and lying 24 yards (22 m)). The stick design also minimized the risk of the grenade rolling downhill back towards the thrower when used in hilly terrain or in urban areas. However, the additional length of the handle meant that fewer could be carried."

Kind of stemming off of this, I remember hearing that the shape of grenades was influenced by the sports the nations played. Americans played baseball, and Brits played cricket, so they were more used to throwing spherical objects.

Does this have any validity? Or is it just urban legend?