Whenever I see a weak player get to showdown with a flopped monster it always amazes me how little they win from the pot. The fact of the matter is No Limit is all about winning the most amount of money that you possibly can with the best hand. Bad players think the best way to do this is to trap—good players know better.
You have to build a big pot yourself to win a big pot. It is simple math—if you bet 75% of the pot on all three streets you will win a much larger pot than if you check the flop and then bet 75% of the pot on turn and river. You have to evaluate the texture of the board when calculating your flop sizing. Let us say for example that you raise UTG + 1 with 7♦ 7♠, three people call and you see a flop of A♣ K♣ 7♥. Not only is this board draw heavy but also when you flop middle or bottom set on high boards you should probably bet heavy against multiple opponents. People will give you action with top pair. This is different than having say 6♦ 6♠ on a 9♥ 2♦ 6♠ board. For the most part people are not going to put in a ton of three street money here with a hand like K♣ 9♣. However, when people flop top pairs that are high, they are more likely to hold on because those top pairs usually remain top pair by the river. This is also why low boards like this are so prone to semi-bluffing especially against bettors that were not the pre flop raiser.
So with this bottom set let us say that the pot is $60. We bet $40 and get called. The turn is a harmless card and we bet $110. We are called again. A brick falls on the river and we bet $300. Our opponent reluctantly calls with AQ. Our big bets were certainty set up by the fact that we bet big on the flop. If the flop was checked through we probably would have bet $40 on the turn and $110 on the river losing out on $300 worth of value. You can see how missing out on early street value leads to an exponential loss by the river.
In capped games and in smaller buy in tournaments you can sometimes afford to miss one street because stacks can get all in by the river anyway. However, if you are playing in a typical game with 100BB stacks and the preflop sizing is less than 5x, you will need to bet every street in order to get all of the money in by the end of the hand. The deeper that you are the more that you have to bet on each street.