Is there a reason why you can like your own post?

Facebook, Instagram, and Twitter all enable you to like/favorite your own post. Is there a reason behind why they allow you to favorite your own post? Should it be done an alternate way?

There doesn't seem to be any real negative since you don't gain anything from the like directly. At the same time, the purpose of a like is to either help filter content for your preferences, share stuff you like with the people who follow you, and to show support to the poster. None of these apply when you like your own post. Why is this a feature?