Willie's First First Down

The NFL season started tonight, with the Thursday opener between the Dolphins and Steelers. I'm going to give the refs a pass tonight, although I will mention that the pass interference call when Charlie Batch overthrew Cedric Wilson that led to the TD to make it 14-7 was absolutely ridiculous. Since when did hand-fighting on an uncatchable ball result in PI?

Today, I'm going to address Willie Parker and his inability to just go back to the huddle. The Dolphins did a good job containing him for most of the first half. Then, he caught a little dump off, out ran one defensive lineman to the corner and cut back inside another and picked up a first down. Rather than head for the huddle, he got up and did a little celebration. A subsequent run went for a first down and he did another little celebration. Maybe he learned it from everyone's workman WR Hines Ward, who does mocking celebrations in the end zone and also toots his own horn after routine catches.

I have two questions: 1) why do the Steelers players feel they need to celebrate like this? and 2) why does the league allow it if they don't allow entertaining end zone celebrations? The Steelers are annoying; TO is entertaining. I'm confused.