not sure how many conferences you have been to, but (1) abstracts are filtered, since conferences probably get 100s of abstracts for every slot they have availa

not sure how many conferences you have been to, but (1) abstracts are filtered, since conferences probably get 100s of abstracts for every slot they have available, some of which end up being converted to workshops or breakout panel discussions to accommodate interesting topics, and (2) I've seen presentations where "lively" discussions have happened between the presenter(s) and the audience.