We often assume that they know what we want or if we have told them before that they know. Sometimes it takes several times and several methods to communicate your desire in order for your partner to get it. Before you think that too unreasonable, know that the same holds true with you - in other words, your partner sometimes has to communicate to you their desire several times and in several methods for you to get it!
And please let's put that unrealistic and irrational belief to bed that if you have to tell your partner what you want and then they do it, it really doesn't mean anything. WRONG! It might just mean that they love you. After all, love is wanting the best for someone and being willing to take action to see that they get it..
Principle: Couples are happiest when each is doing many of the things the other desires (Paul Hauck).
We are all motivated by "what's in it for us". If both partners are taking this attitude toward one another, each is much more likely to be satisfied with the relationship.