Most managers have a secret need to control, to be in charge. They feel they've worked hard to get where they are and they deserve to call the shots. They worked for a lot of bonehead managers in their day and survived and now they want to even the score and drink from the cup of power. Their actions say "Look at me--I made it and now you have to do what I tell you to do! Even if it doesn't make any sense! Because I said so!!"
Of course, employees today rarely interpret their managers' control needs as signs of well-deserved honor and respect, bowing to their sage wisdom accumulated over the years, but instead react with "Why's Gary being such a jerk?" and conclude that Gary must have indigestion or is upset perhaps that someone dinged his car in the parking lot.