Are you seeing this a lot too? It makes no sense to me. IME small businesses can be terrible employers with questionable hygiene practices and corners cut to save the owners money.
McDonalds on the other hand is a very fair employer, pays well above minimum wage for the kinds of jobs that would attract exactly minimum wage elsewhere and is absolutely hot on hygiene.
These posters talk about supporting small businesses because that "pays for a little girl's dance lessons" etc, do employees of bigger firms not buy dance lessons?
Obviously people should spend their money as they see fit but the big companies are important to the local economy too and (usually) became big companies by being very good at what they do.