Or maybe they realize that the 20th dog, who receives no bone and has to watch the other 19 enjoy theirs, might become angry and start causing problems. The 19 dogs, realizing that group performance and cohesion is far more important than 1/19th of their individual bones, all donate a small portion (1/19) of their own bones.
Conflict is adverted, and every dog continues to work together, as they all feel like participants in a mutually beneficial relationship between themselves as individuals, and the group as a whole.