It's still common to use phone number to input location for car navigation because its Japanese input system is not good. Phone number is easiest but sometimes points wrong position if you use older maps. We won't use it on smartphone's map app.

~2 years ago. Navigation of rental cars worked best with phone numbers. Some cab drivers also preferred phone numbers. Most likely some service to lookup phone-number->GPS became popular - I haven't seen this outside Japan so far.