Some dragons are fiercely territorial and will attack other dragons on sight! However direct confrontations are rare in our modern age, mainly due to the rarity of dragons and their desire to remain secretive. Mankind’s relegation of dragons to fantasy has greatly aided their survival. They don’t need a noisy, fiery battle making people aware of them. No one is sure how large a territory a dragon needs, but a ready supply of food, water and treasure is a must.
There are few things so happy as a well fed dragon. The smaller you are the easier you are to fill.
So it lends itself that the smallest dragons are the happiest, and none so easily pleased as the egg eating dragon. Chicken farmers beware!