Yes, I realize that. The article upthread from Der Spiegel goes into that in detail. That may be valid for commercial operators like McDs and Starbucks. However airports, rail and bus stations, etc. should find an acceptable way to at least allow people to access their own and related websites so as to get flight information, timetables, news, weather, tourist information, access standard webmail like gmail, hotmail, etc.
Better still there should be some way for visitors to get an access code without requiring SMS. For instance on a recent trip to CH when I told a hotel desk clerk that I couldn't use their free WiFi because I didn't have SMS service she pulled out a stack of cards, each with a unique access code. Granted at a hotel they know who you are. I would have no problems with showing a boarding pass or ID at an airport, etc.
Added: Or accept a credit card but charge a
nominal fee like €1 per hour. If they're willing to offer free WiFi to those with SMS service then why gouge (€5+ per hour at DE airports) those without?
It seems that
CGN Köln-Bonn airport is the only DE airport with truly free WiFi.