You have to choose the target bird to lay eggs on, so it's hard to just have it on by default. The game could add a feature where it's automatic by default if there is only one option of where to lay the egg, but asks the player to choose if there's more than one choice, but that's a bit more complex so it would require more thought and coding, not just a simple flip of a default setting. I think there could be improvements made in the ability to automate egg-laying pink powers, so if you have thought about the details you could post on the suggestions forum and then comment here with a link.
As for discoverability, I think that applies to other bird powers too - I think many players won't notice the ones that default to off can be changed, they may just think some bird powers are now automatic while others are not. If someone has a good idea for how to ensure more players find out that they can turn these on or off, that's worth posting a suggestion for also.