For the same reason that Elizabeth Warren says "Latinx" despite a tiny fraction of Latino citizens identifying with the term: many of them are running for what's been described as "President of Twitter", where Twitter is a metonymy for old-economy institutional elites, lashing out pathetically at the democratizing forces weakening their hold on power. I assume the reason politicians do this is partially drinking the Kool-Aid from their bubble, and partly intentional pandering to journalists who are also in that bubble.