One reason that people make cynical, deceptive claims is that it doesn't impact their credibility later. The next thing they say, people don't respond, 'well you deceived us last time'; when the honest person says something, others don't give them much credibility.

That little bit of morality - truth, honesty, integrity, etc. - is essential to a functioning society that leans toward good outcomes. (Often it seems that many just assume we'll get good outcomes, not that they must work hard to make it happen.)