using postgresql for session

has anyone used postgres jsonb for holding session ?  Since server side
session is really just a piece of data, why bother with special
"session" plugins and just use postgres to hold the data and retrieve it
with psycopg2 ?  Maybe use some trigger if session changes?    We are
using python Bottle with psycopg2 (super simple, powerful combo) - are
we missing something magical about session plugins ?