What is with the Pajama Bottoms!

So, last week I was in our neighborhood grocery store and I noticed that more and more adults seem to think it is acceptable to go out in public in pajama bottoms. What the heck is up with this?
They look like vagrants that have escaped from the local hospital. When young girls wore pajamas in the public, I though it was a bit strange but cute. Now it is a plain scary seeing a grown man walking around in his "jammies," in the produce section. Just who do they think they are? Hugh Hefner! Put some clothes on!

***UPDATE***I decided to try this out. I went to Kroger's in my pajamas and I noticed no one seem to pay attention except my exchange student. As I was walking from my car into the store she said, "oh you have your pajamas on, are you going in?" I said, "yes." She said "in Korea we think only crazy people walk around with their pajamas on." She then told me that when she went back over the summer she went out with her friends wearing pajama bottoms and they though she she had lost her mind." When she explained that teens do this in the United Sates they thought it was a bit cool! Just think next year our biggest export to the fashion world could be going out in public in your pajamas. The French give the world Haute Couture, the USA give back pj's.