This baffled me, too, but here's the answer:
In h17, the dealer busts more, so your doubled bet makes more.
When you double, you give up the opportunity to get a fourth (or fifth, etc.) card and a fourth card isn't worth much when you're hitting a stiff hand against an A (and A6 could be bumped up to 18, 19 or 20).
In s17, the dealer busts less, so your doubled bet makes less.
That fourth card is worth more, because there's a chance (1/13) that it only challenges an A6. In h17, that chance is zero.
These differences change hit to double. By the way, your doubled hand in h17 has lower EV than your hit hand in s17.
Now, in s17, as the count goes up, 11vA gets worse because it ends up as 11vBJ more often. BUT, once the dealer checks for BJ, You get more 10's to give you 21, and the dealer's most likely next card is A. (The dealer is also more likely to get two more 10's and bust with 22, but this help is actually tiny.)
To start with, it ends up that you make less money when you double in h17 then when you hit in s17.
In h17, the dealer busts more, so your doubled bet makes more.
When you double, you give up the opportunity to get a fourth (or fifth, etc.) card and a fourth card isn't worth much when you're hitting a stiff hand against an A (and A6 could be bumped up to 18, 19 or 20).
In s17, the dealer busts less, so your doubled bet makes less.
That fourth card is worth more, because there's a chance (1/13) that it only challenges an A6. In h17, that chance is zero.
These differences change hit to double. By the way, your doubled hand in h17 has lower EV than your hit hand in s17.
Now, in s17, as the count goes up, 11vA gets worse because it ends up as 11vBJ more often. BUT, once the dealer checks for BJ, You get more 10's to give you 21, and the dealer's most likely next card is A. (The dealer is also more likely to get two more 10's and bust with 22, but this help is actually tiny.)
To start with, it ends up that you make less money when you double in h17 then when you hit in s17.
