My guess would be that they just never considered that there would be first world countries without cheap mobile data everywhere.

When I was living in Asia, even in poorer countries and/or rural areas, there was mobile internet. $1/mo for 4G 1GB. People took it for granted at a level that would be impossible in Germany, because here you can still be without even 3G just a few km outside of city centers.

Also, mobile internet repeaters for tunnels are a solved problem. Singapore had no offline areas in their underground metro. Germany has lots of em.