DL where is the spirit? No Halloween Costumes allowed?

I have seen some great Halloween costumes worn by DL employees over the years (UA as well). This year I went to check-in at DL and no costumes. I asked the agent and he said DL put up a notice no costumes, hats, etc. are to be worn on Halloween. Why?

All I can think of is branding. Perhaps safety?

Did anyone see DL agents wearing costumes in any DL city today? :confused:

Happy Halloween! :)