That buildings shield reception is not a political issue but a physical limitation.
When I'm in my super market I know that I will not have reception in the back, same in the underground part of my fitness center.
Apparently it's not. I live in Finland and I've never had my internet connection cut off in a supermarket (or any other large building). This has happened to me sometimes in Southern Europe, though. I don't know if they boost the reception somehow in large buildings here or if the building materials are just somehow different.
It's mostly your random good luck and other people's random bad luck. A lot of building design choices can result in severe signal attenuation in microwave range, and not all buildings will have internal femtocells to cover that - or femtocells that accept your SIM.
Also, some buildings change over time in how they attenuate, especially freshly built ones where the walls are still "drying" can have close to 0 reception inside. When my parents built their current home, I had to keep an informal map of where the signal was strong enough to use GPRS (yay 7s ping in MUDs) and for voice we usually went outside.