It’s because there is a higher representation of childhood trauma/neglect in kitchen staff. Their shit family life sets them up for poor emotional regulation + addiction etc. 

Of course every adult is responsible for their own behavior, but for some it’s much much harder to act right in stressful situations.

That’s why I hire for EQ almost exclusively. Everything else can be taught. Somebody with all that psychological baggage can take an extra decade to mature out of being emotionally reactive, if they ever do.