[rzk]

without debating the merits of 3betting with your monsters vs waiting till the river, the villain certainly doesn't know that you will be waiting till the river with your monsters. at $3/$6 people put in action on the turn with monsters much more often than they wait till the river without thinking too much about it. so even if you are right that's not really relevant for the current hand.

also, i have no doubt that 3betting or capping with a draw happens all the time in higher stakes games, but this is $3/$6, which plays quite a bit differently.