zaps are useless for human interactions where people are "on the same level" and contribute respectively in the same measure to the conversation. People pay other people in exchanging of speech when there is a knowledge mismatch (pay a teacher to teach you something) or a sort of different "pleasure mismatch" in partecipating to the interaction (pay the rockstar to entertain me) and so on.... In most of the case speech works without money and theres no "incentives to fix" about that.