I'm not sure when this happened, but the new (ish?) bit.ly homepage is not at all one that I would expect from a URL shortening service. The box to actually shorten a link is small and tucked to the side, instead of front and center like you might expect, and the user's eye is now instead drawn to links to sign up and log in.
I would be willing to bet that a large percentage of their traffic is from users who are not registered on the site. While I understand that they're expanding the platform functionality and trying to reverse that trend, the new design still strikes me as straying from the core offering and not focusing on what most of their users are looking for.design