According to most Basic Strategy, you would hit on a hard 16 when the dealer upcard is a 7,8,9,10, or face card, including Aces. The thinking is the dealer most likely has a ten in the hole, and you will need to improve your hand to win. Sure, a lot of the time you will bust, but statistically it's better to hit.
When holding nine or less or 12-16 it's best to hit, but stand on a total of 17 or more. If the dealer's card is a four, five or six it is vital you do not bust. It is common practice to hit on eight or less, but stand on anything 12 or higher.
