Stupid Question

I have an extremely stupid question: why do you stand on a 16 against a 10 in a positive count? Isn't the dealer just as likely to have a ten in the hole as you are to get one on the hit? Also, why do the blackjack authors say 'A positive count is good because the dealer has to hit his bust hands-you don't" while the counting indices generally only say to stand on 16 in a positive count- the count has to be like +80 to stand on a 13.