Musicality and timing are EVERYTHING! It doesn’t matter how great you look, how many turns and spins you can do, how flexible you are or your great posture, it doesn’t matter how fast you can move, or how great your styling and footwork are IF they are not done on time with the music. If musicians did not have any timing then they would not be able to coordinate the music that they create, therefore you wouldn’t have songs. As a dancer, if you are not dancing on time with the music, then you are not dancing (although it might look like your dancing, your just randomly moving to no beat).

When you are dancing by your self, you as a dancer have an established relationship with the music. When you are dancing with a partner, you have a relationship with your partner, and what is holding that relationship together is the music you both are listening to. When you are not dancing on time you loose that connection with the music and the experience of dancing becomes shallow. It then becomes just random movement. The equivalent would be of someone banging on the drums (Or playing whatever instrument) with no rhythm, it holds no meaning; it just then becomes random noise.

On the contrary, when you are dancing on time with the music it is the equivalent of making music, with your body. The dance becomes MUSICAL. You are being music, and the experience is much deeper. Plus, when you master timing more people are going to want to dance with you because they can make sense and follow what you are doing. 

Here are 2 videos that will help: