Why is spam more than two of the same anything? Maybe it would be better called redundancy. Certain armies need copies of units to get the job done. One of my friends has a huge collection of IG and he usually takes three of everything and still sometimes the units wont accomplish their assigned tasks. Same thing with Ork and Nid troops, you need massive amounts of the same option especially if you running on foot. The only army I think can't get away with spaming is Space Marines and thats because you usually only need one of something to get the job done, maybe two.