My line of thinking was two-fold:

-by the turn, a weak draw or face cards aren't going to call a turn bet.
-if I let either of them catch anything, I'll make up the bet.

The problem specific to my hand (that I posted in the other thread) is that the board paired on the turn, so even the flush draw isn't going more than a bet or two on the river.

On your hand, you can expect a gutshot, overcards, or a 7x to AT LEAST call a flop bet. Then, checking the turn isn't ALWAYS bad against:

-Ax because now he doesn't necessarily believe you had a 9 and will call a river bet
-7x-same as above (and he'll probably go 2+ bets with you).

I guess, in SOME situations, a turn check with a strong hand can buy you an extra bet in the river similarly to the way a semi-bluff with a strong draw on the flop can buy you a free river. I don't buy into the concept that one should ALWAYS bet the turn rather than slowplaying