I know, this is going to sound "extreme" to most, but consider, for a moment, the analogy.

Imagine having a prized possession. That is how I see a slave to a Master but this analogy can also be used in the D/s context, as well. When one has a prized possession, like say a classic car, one takes the best care of it possible. One makes sure that it is sensitive towards what it is telling it. The classic car may not be able to literally "speak" to it's owner, but it can and does give the owner certain signs whether it is in good shape or when it is in need of some major or minor care and repair. A good owner "listens" to and "watches" his car, he doesn't just stick it in a garage and then take it for a joyride and then stick it back in the garage without checking on it once in awhile. He gives it the best possible care. Why? Because the car and how he keeps it is a reflection of HIM. If the car is in bad shape, it reflects upon his ability as an owner of the car. If it is kept in great shape, he is honored and much pride comes from his car and the car will serve him the best it can for a very long time. And, in fact, he does all he can to make sure that car lasts in top condition so that he can enjoy it for as long as possible. I see it much the same way, with BDSM relationships. (Long and short term.) A sub/slave does need to communicate to her Dom(me) or Master/Mistress but in the same way a Dom(me), Master/Mistress needs to also be sensitive to the nonverbal as well as the verbal communications and make adjustments to get the most out of the relationship not just for himself but for the sub/slave because it really does reflect poorly upon that Dom(me), Master/Mistress if they don't.