Pondering a bicentennial half dollar from change at a fair

This weekend I traveled to the town of Bloomsburg Pennsylvania to visit their annual fair.  Eschewing the customary bloomin’ onions and gastronomical disasters such as deep fried Pop tarts, I indulged in Thai foods including coconut lemongrass soup, squid in hot, sweet sauce, and Pad Thai.  For change, I received a bicentennial half dollar, which appeared to my well-trained eye to be still in the mint state (probable grade: MS60). 

Since over half a billion bicentennial halves were produced, getting one in change should be nothing unusual.  It was however, the first half dollar I have received in years.  (I still haven’t received a presidential dollar in change other than from a vending machine -- but that’s a ramble for another day).  Kennedy half dollars are no longer made for circulation -- but instead, only appear in uncirculated and proof sets .  The value of the US dollar has deflated since the 1970’s.  Therefore, we might expect that there would be more need for higher denomination coins such as the half dollar and dollar.     Instead, the largest denomination that seems to circulate is the quarter.  I pondered this while I ate my soup.  To me, this is counterintuitive.  I welcome your possible explanations and hypotheses.