What's up with all those tip jars?

[Fountain79]

Am I alone in taking pointed notice of all the tip jars that have blossomed on business countertops? From delis to pizzerias, Chinese takeout joints to barbershops, the word has spread like wildfire: If you put out a tip jar, people will fill it. Well, maybe they will, but I have yet to be shamed (if this is the right word) into casting my coin into the tip jar fountain. Perhaps it is the scientist in me, but I try to reason the situation out like this: I call in my order to the Chinese restaurant. I drive there to pick it up. I pay the menu price. Why on earth would I pay more than they are asking for their product? Doing so strikes me as positively un-American.

http://articles.moneycentral.msn.com/SavingandDebt/ConsumerActionGuide/WhatsUpWithAllThoseTipJars.aspx

I have noticed this myself. There are numerous fast food/take out places that I can think of that seem to revert to this practice. It seems odd to me.