I don't know how many times people I've danced with have told me this! Whenever I'm dancing with someone who is at a higher level than me, I tend to look at my feet just to make sure that I'm doing the moves right. I'm sure many other people feel the same way.
What we do not realize though, is that we are so focused on getting the steps right that we don't allow ourselves to be led properly by our partner. Yes, knowing the steps is important but being able to follow as females is even more important. It doesn't matter if you're doing the moves perfectly or not, it will not look good if you don't follow your partner when he leads you. Obviously the more advanced you get, the better you get at being able to follow and thus relying less on getting the sequence right because you know your partner will just lead you into it.
Another problem with looking at your feet when dancing is the loss of eye contact. It is important to have some sort of connection when you're dancing with someone. Chat. Smile. A bit of eye contact is important. Of course too much eye contact can get a bit awkward too especially if you're dancing with someone you're not familiar with. It all comes down to balancing your eye contact though.
As dancers in ballroom dancing or any other partner dance, it is important to have eye contact because it is a tool that helps you connect and communicate with your partner without speaking. It is therefore a good idea to practice and master it. Make it a natural thing and make it a habit when you dance. This discipline is really more of an art form within the art of partnered dancing.
And remember, making eye contact and giving a smile also makes your partner more comfortable. You're basically letting them know you want to be there and you're enjoying yourself. if you make you partner comfortable, they will probably make more of an effort to do the same for you.