I occasionally challenge myself, and I am always surprised how much more active my mind is, compared to GPS where my mind is passively glancing at the screen every few seconds to see if I'm on course and next turn.
If you don't navigate you lose spatial awareness over time, I know some people who can't tell you how to get to their job from their house.
It also helps to build up a mental map of the city I live in, which I find to be one of those skills you can learn which feels like a bit of a superpower. Being able to find and navigate along a route, deal with detours, or navigate yourself around congested areas.
Recently I was trying to leave a large complex parking area when we noticed it was gridlocked. We were able to navigate a way out the back that hadn't become congested yet, and save ourselves from 4+ hours of waiting and ending up on the news.