There is a quite a large difference between the two.

Calling is an active interest. It requires specific action from the caller, and potentially interrupts the callee (which may or may not be desirable).

Facebook and other social media allows a more passive interest. The information about how the person is getting on is passed on, but the "caller" isn't needing to worry about disturbing the "callee" and the callee is not interrupted.

Sometimes we don't call because we don't care, we don't call because we don't want to impose.

This passive information forwarding replaces to an extent the part of the "village" culture that has been lost a bit as our populations have grown more and more densely packed yet the people we care to "follow" are often spreading geographically further apart. Because not everyone knows everyone, the "oh, did you hear" conversations don't spread as they once did: there are wider air gaps (filled with signal noise, i.e. the rest of that dense population) between the connected nodes in the network.

Of course social media is emulating the worst parts of that village culture grape-vine, as well as the useful parts...