1) Because on a card/board that favors your range and not your opponents range you want to valuebet all your good hands. You want to bet all the other hands as well due to the fact your opponent just does not have enough good hands often enough to continue, and if villain continues you do not gap your range and can keep repping certain range on later streets.

2) Well, I ll just make up a random example.

6max NL

UTG reg opens, everyone folds. you are on BB and decide to call. Flop Comes 864ss.

Now thinking about villains range, he/she should not have too many sets, villain should have all the overpairs, no straights, no two pair. You on the other hand should have all the sets, a lot of 2 pair. atleast 4 combos of straights, way more 7x, 5x. So Leading or x/raising a huge range makes sense. You should know most regulars rangecheck this board for the exact reasons, that is why having a leading range on the boards that favor you makes sense.

Like in a 3bet pot in PLO the turn is an Ace and there are no straights or flushes out there its obviously a great card for the PFA-s range since he can have all the AA combos.

thanks boutthreefiddy !
The main issue I am struggling with is this: why is the money you gain from bluffing in these spots not offset by the amount of value you miss-out on when you have a value hand?"
After thinking about this some more, it seems to me ( and I may be wrong) that we are ignoring any extra money (over the size of the existing pot) won by bet itself ( we are supposed to make villain indifferent), so betting boards that are good for us is more about taking the pot down than getting additional value. Is this correct?

Its the most efficient way to maximize expected value. That's obviously the goal.

In other words, why is the money you gain from bluffing in these spots not offset by the amount of value you miss-out on when you have a value hand?

That is probably not true. I will speculate you make this argument, because you feel like your not getting enough value from your strong hands, when you bet big in these spots and your opponents are folding very often?

That is a reasonable point to make, but the solution you come up with is putting the cart before the horse. You shouldnt bet smaller to get more hands to call, but rather need to include more bluffs in these spots to gain EV from your opponents folding. In turn your opponents would need to defend wider, which is difficult for them, because you have so many good hands as well.

Think about it the other way around: In situations where the board does not support your range at all, you instinctively bluff less hands, because you know that you get called/raised a lot and therefore loose money. In this case your range does not have enough value hands to support you betting a lot of hands.

Assuming GTO, eventually both of you will reach equilibrium where your EV is positive in the first example with how the hand played out given that you are in a advantageous position range wise. Villains EV in equlibrium is negative, but he is minimizing his looses as good as it gets, because he is calling just the right amount of hands. In the second example its the other way around.