Is mobile internet actively suppressed in or near supermarkets? [closed]

I’ve lived in Germany for some time, and noticed that in almost all supermarkets (rewe, müller, ikea, etc) i have bad or absent mobile internet. Also, I live near Rewe, and when walking nearby, my mobile internet almost evaporates. When I lived in other countries, such behaviour of mobile internet was rather the exception than the norm. It almost feels like that it is being done on purpose, by actively suppressing the signal strength (or whichever other ways possible). Is it the case?