I wanted to make a callable bet there. Despite this guy being pretty LAggy, I felt like thumping the all-in button would send a message: either "I'm really strong" or "I'm bluffing like mad." I felt like I had a better chance of him calling $15 than calling the all-in, which wasn't much more expensive. If he did call the all-in it would be because he thought I was trying to bluff him out... rather not take that chance. He had bet $15 on the turn already so I suspected that if he had any kind of hand, he would call that same bet on the river.