I umpire both sports, and I find baseball to be more challenging at the higher levels.There is more to do and watch at a quicker pace in softball. And you would be surprised how many baseball umpires, even in the pros, kick calls and interpretations.
Plus the potential injury factor to the umpire is much greater than in softball.
( Just look at the protective gear required in baseball as opposed to even high level softball.)
My point is that a lazy man may be more drawn to doing softball as to baseball under the perceived impression that softball is a piece of cake.