Rather than saying they aren't good at math a better way of putting it would be they are using a different objective function for their decisionmaking from you.

Rather than saying they aren't good at math a better way of putting it would be they are using a different objective function for their decisionmaking from you. The marginal utility decrease from buying a ticket is close to zero for many/most people whereas the marginal utility increase from winning $2bn is essentially infinite. So the motivation for buying tickets is pretty clear in mathematical terms as long as you optimize expected marginal utility rather than expected value.