You just assume that AIM would be better as a "social network".. but not everyone wants that, some people just want simple chat.
In fact many people think google's failure with gchat was trying to force people to use things they didn't want when all they really wanted was simple chat.
The point is that AIM was a social network before the idea was even conceptualized. The concept of a friend activity feed existed on AIM in an ad hoc manner before it was hard coded into facebook/twitter/etc: it was standard to go down your list of friends and see who was doing what based on their status message. If someone at Aol had any foresight they could have been on the ground floor of the rise of social networks.
Aol was used as a simple social network. Checking people's statuses was common practice back in the day. As was changing it. Same with your away message. Also being able to see idled people was helpful. None of these features are available or used much in modern mobile messaging. Not sure if WhatsApp status messages (not their story feature) is actively used.
In fact many people think google's failure with gchat was trying to force people to use things they didn't want when all they really wanted was simple chat.