The Mid West just seems to be a more "informal" place nowadays. The only people you see in suits are the old men who were raised in that scenario. Most folks my age wear jeans and a polo/button down, and think that's enough. I've always enjoyed dressing up, but like BB, don't want to outdress the groom.
Now, I wouldn't say that so quickly...I know a number of "young'uns" in our St. Andrew's Society here in the Midwest who wear suits/blazers etc. to various functions, myself included.

T.