As with most things when it comes to Democrats, it is not about minimum wage. It is about votes.
If they can convince more people to vote Democrat even as it destroys the economy, they will do so.
We now know the Republican party is the Washington Generals to the Harlem Globetrotters.
Beyond just a play for votes, this is also part of the Social Security fix; those workers will be contributing more to SS (and income taxes). It is putting more of a payroll tax burden on companies as well (who have to match the SS).