[Crumpled Ear]

Can someone explain to me why the charts bother listing odds for completing a hand when both the turn AND river are still to come. In other words, why do books often have two columns--one for odds of making a hand with turn and river to come, and one for odds of making a hand with river to come. Don't I have to make independent decisions on both the turn and the river? If that's the case, why include the first column in these tables? Here's an extreme example: let's say I have a pair of 8's in late position and six people, me included, call a raise. There are 12 small bets in the pot. The flop does not have an 8. Now, those tables tell me my odds of catching an 8 by the river are about 11 to 1. As such, I'm encouraged to call a bet and see the turn. On the other hand, my odds of catching on the turn are about 22 to 1. This number, it seems to me, is the one I need to pay attention to. Indeed, if an 8 doesn't come on the turn, I almost certainly won't have odds to see the river. With that in mind, why even pay attention to that first column that tells us odds for turn AND river? Why do books include it?

Thanks!