DC has great public transit so

1. You probably didn't need to bring your car. Also, the speed limit can be pretty low in certain areas so in many cases it's better to be riding an ebike or scooter, and ebikes and scooters don't cost like $14k/year.
2. DC has great public transit so generally the expectation is that people will get home on their own. Expected social dynamic is that people get home on their own. Uber can be expensive but Metro is $2-6 one-way. People are tripping if they can't afford $2-6. I'm assuming here that your friends aren't particularly poor or anything though. The main exception to the expectation I mentioned is places that aren't Metrorail and Metrobus accessible.