Making a girl cum is a bit of an art form. It takes more than just a hard cock to get the hottest pieces of ass off. They're used to be desired, pursued, and fucked. They aren't used to being dominated and teased. When they do finally feel the intense satisfaction of orgasmic release it isn't going to be some little tingle in their nether regions. It's going to be an overwhelming explosion of erotic energy.
AJ Applegate, for instance, is a hot blonde that looks like she could have any man she wants. Stick her in a bar and she would have guys falling all over themselves for her attention. But here in our dungeon there is only one man, and she probably wishes he had something else to do, other than tie her up and torment her.
She doesn't know it when it starts, but all of this pain is just to enhance her pleasure. It gets her juices flowing and releases the kinds of endorphins that will push her orgasms over the top. Then she just has to wait for Jack Hammer to decide that he is ready to give them to her.