Jeans day?

Did someone neglect to inform me that it's jeans day today? Generally, we aren't allowed to wear jeans to work, but my boss is wearing jeans. And an intern on our floor is wearing jeans.

Since leaving my last company, where the dress code was "casual," and workers were sometimes spotted in questionable (in my opinion) attire, I've missed wearing jeans nearly every day to work. I think I push the limits of our "business casual" dress code by wearing wrinkled khakis on days that I don't have important meetings, but I still yearn for the days when I could wear a pair of jeans to work.

What is it about corporate America that frowns upon comfort and expressing individual style? Why must everyone conform to boring clothes that strip you of any or all personality? What is so offensive about denim, anyway?