This becomes especially apparent when you're in a country with a different language and alphabet (Greek, Cyrillic, Chinese, etc). Even if the device successfully pronounces it, you can't look for it on street signs.
I think car navigation and looking at the map are different ux activities though. When you're navigating a car, the street names may not be useful, but when you're walking with a map you can certainly compare what's on your display and what's on the sign (whether it's Latin, Greek, or in hieroglyphs) without knowing how to pronounce it.
When driving in some countries in Europe a GPS will repeat that you should use <really long badly pronounced street names after an old white guy> for multiple steps when in fact the road signs don’t mention the street anywhere and just say “Center”. (Granted sometimes the GPS directions are correct and use signage info.) Or the street name may have changed 5 times, as you keep driving straight on the same road.
The problem, as with all things in maps, isn’t so clear-cut and the fixation on street names is very centric to certain countries.