Its way more risky to bluff when lead into then when checked too.

Senario #1 Your in position, your on the draw but the river comes a brick. Its bet to you, too bad you fold. You could raise, but it looks like hes making a value bet and is trying to get every penny he can for what hes holding, he could just have top pair but as far as you know he has the nuts.

Senario #2 Your in position, your on the draw but the river comes a brick. Its checked to you, he either missed his draw or hes worried about what you have. A bluff might take this down after all.

Senario #3 Your in position, your on the draw and make it on the river. Its bet to you, perfect. You consider what your opponent is holding and try to make a nice value raise that hes likely to call.

Senario #4 I went all the way to the river with 22 trying to spike a 2. Its bet to me but Im a donkey and try to win every single pot. Im not even going to consider what hes holding, All-in