Ballistic repeatability. Semi-spherical, equal weights, it flies about the same distance each shot.
And the trajectory would remain as intended. Also, if it bounced, it would roll back to be used again. ;^)
Good point...Aerodynamics too. I’m thinking also the damage after it lands if it keeps rolling.
The of course, the device itself, is made to accommodate a certain size and weight ball.
And then there’s the crating and transport.