It is true that you can get sick at any place where there are many people, supermarkets, schools and workplaces are all full of people sniffing and coughing. The difference is that noone feels obligated to go when they are unwell and these places also have strict policies about whether sick children can attend. I never felt guilty about not going to Walmart if I was sick.
This is actually a serious issue since elderly people exposed to viruses can become extremely ill. For years it was seen as essential to attend meetings and only stay home if you were bedridden or severely incapacitated. This meant that people brought themselves and their children to the hall when they would be better off at home. Not just better for them but better for everyone else as well. Since many halls have no windows, sitting for two hours in an enclosed space with the air recirculating means that there is a strong likelihood of infection spreading.
When swineflu became an issue people were told to think of the elderly and stay home if ill. I sincerely hope that people show common sense.