The Local Guides community plays a big role in providing Google with this data.
Sometimes, with all the fuss about the things Google does poorly, we forget that it's filled with people who want to make the world a better place. For some, that means building balloons that can deliver internet service to places with zero infrastructure. For others, like Sasha Blair-Goldensohn of the Google Maps team, it means helping everyone get more from life.
Sasha is in a wheelchair and lives in New York City. Having visited New York City on several occasions and being in a wheelchair myself, I can only imagine the logistical nightmare that public transportation and -- more importantly -- public access is for him. That's why he's trying to make a difference by building accessibility features like wheelchair-friendly directions into Maps.