It's exactly because humans contain multitudes that teams use personas. You can't design your ridesharing app around the needs of Marco, the policy coordinator

It's exactly because humans contain multitudes that teams use personas. You can't design your ridesharing app around the needs of Marco, the policy coordinator in Washington, DC who loves longboarding and doesn't own a car, who needs a way to occasionally get to his aunt's house in Frederick, MD and also to get home after a wild EDM show - that's way too specific. What if Marco only wants to ride in American-made cars? Other people who need transport might not care about that. Instead, you can design your app around "person who lives in the city, doesn't own a car, and needs transport for trips outside the city ~3x/month," and "bar/concert patron who needs transport for trips within the city ~5x/mo and may be intoxicated when trying to purchase that transport." A "persona" is a shared part of the human experience that your product interfaces with, and using that abstraction lets you create products that fit neatly into many people's lives.