I honestly am not an expert on it but often times it is about the taboo aspect of it. Some persons get excited by things that seem unacceptable. The other thing is it becomes more of a physical thing then an emotional and spiritual act. I imagine that your partner may be trying to keep the level of interpersonal connectedness at a minimum. It's about the pleasure and the pain which are all physical sensations, numbing or masking the vulnerable side of sex. Please don't go and bang your significant other over the head with the "You just want to have sex like animals and I wanna feel some emotion in it.", because that may not be the case. I think it is fair to expect some compromise in the way you two interact. I would hope that he would validate you and your wishes enough to engage in intimacy in a way that is more then a physical act. I hope this helps facilitate some communication between you and your partner and that you can grow closer. Good luck