I have worked in both loose and strict attire environments. In the loose environment, the CEO came to work in shorts, sandals and a surf shirt, and most employees naturally followed suit. In the strict environment, everyone wore at least dress pants and a collared Polo shirt, if not a dress shirt. I heard zero complaints or grumbles. Most people liked the fact that everyone came to work dressed nicely.
The benefits of the loose environment were flexibility and accommodation for dress preferences. The disadvantage of the loose environment, and the benefit of the strict environment, was professionalism.
In my experience, one's attire often reflects one's attitude toward the work. This is not to suggest that strict dress codes cause professionalism, but in my experience there is a correlation. When a person dresses for work they are giving themselves a mental message that it's time to do the job well. It's not play; it's work. Taking off the dress clothes and putting on casual attire signals time for play.
I have seen much higher professionalism in dress code environments than in "cajj" environments.
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