Punxsutawney isn't much of a town, so Groundhog Day is a big deal there. It's a major source of revenue and it's harmless to the groundhog, except that it interrupts his sleep. I can understand a groundhog being mad enough to bite someone. Wouldn't you want to bite your neighbor when he fires up the lawnmower at 7 am on your day off?
The predictions are funny. Sees his shadow = 6 more weeks of winter. Well, yeah. Calendar spring arrives around 6 weeks after Groundhog Day. Doesn't see his shadow = spring is just around the corner. Well, that is sufficiently vague enough that, along with the other prediction, the groundhog is assured of being right regardless of whether he sees his shadow or not.
It's a con job. Town officials shine lights on old Phil, plus there are lights from the news trucks. So Phil is almost guaranteed to see his shadow. Actually, no one is really sure Phil sees anything. Town officials make the declaration. All Phil wants to do is go back to sleep.
It's harmless fun and profitable to Punxsutawney and its businesses. What's not to like?