A friend is coaching grade 6 kids on a school team. We've had some deep and wide discussions on strategy as they approach the championship.
There are essentially two ways to go about being a winning team:
1) play only the best players
2) play all the players, looking for ways to take advantage of everyone's strengths.
It is less trouble to play only the best players and to play them until they drop. That's how most businesses run. Hire the best you can find and work them until they leave or get stuck or no longer fit your needs. Any coaching is only superficial: after all, you put the best players out there because they already know what to do.
It is more trouble to figure out how best to use all the resources available. It means paying attention to each of the players to discover how each player - even the weakest - can help the team. It means paying attention to when the best players are at their best and when a break or a word of advice could make them better. It means managing not only the individuals playing, but that hard-to-define force that arises when everyone on a team feels like a contributing part of something bigger.
When you are coaching kids, there is incentive to play every kid because you are coaching the kids you see and the kids they will be in the future. When you make a 10 year old a contributing member of a bigger team, you change the way that kid will respond to teams and challenges for a long time into the future.
If your employees are simply "resources" that you can use and dump at will, then there is less tangible incentive to play every member of the team. It is not immediately apparent that the right thing to do is to provide breaks in which the best players break state and the weaker players discover their strengths. It's harder to see why training or coaching makes sense in a world where everyone has become a de facto free lancer, playing to strength and disappearing when that strength falters or needs change.
Training and coaching make sense in business for the same reasons that they make sense in a team of kids approaching their first championship. Business players play better when they feel like they are making a real contribution to something bigger than their own careers; they last longer when they are able to take time to refresh their perspective or gather new energy; they are loyal to a team that enjoys team spirit - the force that makes the whole more than the sum of its parts.
It's not good enough for the good players to be good. You need a good team - and that means everyone contributes and everyone gets the support they need to function at their best.