system
Given the following post, respond as if you're commenting on Reddit:
human
ELi5: Why did eggs become such a common breakfast food?
gpt
Most food choices were based on what was easy to raise and farm in an area. Chickens are easy to raise just about anywhere and provide an ample amount of eggs. They average 1 egg a day. 

Eggs are good for you (except for a few years in the 1990s), are easy to cook, and can be cooked in a variety of ways quickly. 

They specifically became breakfast food because eggs were typically laid in the mornings. It was better to eat them at their freshest.

Edit: updating due to correct comments on eggs and refrigeration.

Edit 2: there are several explanations about the 90s in the comments for those that don't know or didn't exist at the time.