I blame relic grind and the such.
Back in 2.0 we used to talk a lot etc in dungeons ( waiting for that replacement in AK because demon wall was too much of a wipefest. ) or cuz ppl didn't know how to wp speedrun etc.
Now most ppl just want a clean quick run to get their tomes/ rewards etc.
Socializing died as soon as they introduced i100 gear imo.