Why is Reddit replacing Imgur?

Good riddance. Imgur was good for a long time. Then they started hijacking controls, pushing their app down your throat, competing with Reddit itself. Their UX went to hell.

reddit should have done this a long time ago, they just didn't because image hosting is expensive in every dimension, and why bother if someone else is willing to do the heavy lifting for you?

Oh right, because they can just become a social network site themselves and eat your traffic. imgur has replaced reddit for a large number of users, and they realize they're losing a ton of traffic to people clicking their way to imgur and then staying there.