Explanation of Social Links
The female members of your party get social links, the males got extra hangout scenes that are new to Reload, but not their own SLs.
As far as what the point of them, it’s really just to get to know the characters if you don’t care about the fusion boost or ultimate personas. There’s no extra abilities for doing a social link.
It is worth doing the social links you like though. The voice acting and character models makes this a drastic improvement from previous versions of P3, and gave me extra appreciation for characters