How does shouting help?

I hesitate to post anything that could come across as criticizing of the Girl Scouts, but...

The last several times I have gone grocery shopping, groups of Girl Scouts (with adult supervision) have been set up to sell their cookies. This morning was one such instance.

When I exited the store with my purchases, the girls were literally shouting the following over and over again (this one time all-caps typing is justified): "BUY 'EM! EAT 'EM! GIRL SCOUT COOKIES!"

How is shouting at people as they enter and leave the grocery store supposed to be helpful? Isn't it more likely people will just find it obnoxious and so be less likely to buy the cookies? Sheesh. I really hope this was a misguided idea by a parent or parents of this one group.