I don't think it's that they are "avoided", BUT instead, since 3 blades kill critters dead, I guess it begs to ask, how dead is dead enough!!
All things being equal, the 4 blade will have about 25% more cut. In other words, compare a 3 blade 1" broadhead to the 4 blade 1", and you get about 25% more cutting surfice. BUT again, how dead is dead enough. 3 blades do pretty darn good and getting the job done!
If the 4 blade flys better in your set-up, that would be a plus for you to use it over the 3!