Why do people put LOL! at the end of each sentance?

Are these people retarded? Here are some recent entries from my friends list on Facebook

I am going to the park LOL!

What is funny about this?

I am making curry tonight LOL!

What is funny about this?

I just got a spray tan LOL!

What is funny about this?

Wine tasting booked for Saturday LOL!

What is funny about this?

What a bangtastic day LOL!

What is funny about this?

Retards.

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