I have had people say to me: "I don't like ballroom dancing because there are too many "rules". The only "rule" we have in ballroom dancing is "to have fun and don't get hurt. The so called "rules" (and many times we do call them "rules") are just suggestions of better ways to do things. Dancers have been working for generations trying to figure out the best way for the two-headed four-legged animal to function.
Ballroom "rules" are the same as for many other endeavors. For example: in horseback riding, the "rule" is to sit in the saddle facing the front of the horse. There is nothing to prevent you from sitting in the saddle facing the horses' tail. It just works better to ride facing the front. The saddle is also designed for the rider to be facing the front and it would be very uncomfortable to sit on it backwards.
A couple of Webster's' definitions of a rule are: "A prescribed guide for conduct or action", "An accepted procedure custom or habit". These so called "rules" are not laws. Laws are defined as: "A rule of conduct or action prescribed or formally recognized as binding or enforced by a controlling authority". There is no authority or enforcement in ballroom dancing. However, there can be consequences to not following some general "rules". For example: dancing against line of dance could cause some physical harm to yourself or others. When dancing lock steps, you need to train your feet to stay pointing in the direction of movement or you could trip yourself or your partner.
Each of the dances' "rules" defines the character of that dance. Waltz feels different than Viennese Waltz, Foxtrot feels different than Quickstep. Rumba feels different than Bolero etc., etc. Without the "rules" defining the character of the dance, they all would pretty much feel the same. This is one reason dancers get bored with patterns, everything feels the same.
One of the "rules" in dancing Waltz for example is "rise and fall". Waltz has a swooping up and down action that characterizes Waltz. Very basically, the foot work is heel, toe, toe and rise happens between 1 and 2 and fall happens at the end of 3. There is nothing wrong with just dancing Waltz flat (with no rise and fall). You just don't experience the true feeling of what Waltz was intended to feel like. It would be like playing tennis using a basketball instead of a tennis ball. You just don't get the feeling of what was intended for tennis.
I always tell students to learn exactly what is being taught by your instructor. After all you are paying your hard earned money for his or her expertise. Work on it until you have developed the feeling of the pattern, element, etc. After you can do it successfully, then you can decide if you want to add it to your dancing. If it feels good, is logical from a physics and geometry aspect of the two-headed four-legged animal and is leadable, then I add it to my dancing. I personally don't teach anything that is not leadable. Sometimes I only add a single piece or element from the sequence taught. Don't discard things just because it is hard to learn. I don't teach things just because they are easy to learn, I try to teach the best possible way even though it may be harder to learn. Learning the hard stuff is well worth the effort. By adding things that we like or feels good to us keeps us from looking like clones on the dance floor.
All of the "rules" are intended to enhance the dancing experience. They define the character and feel of the specific dance, they improve the communication within the partnership, they generate more power and feeling in the two-headed four-legged movement, etc., etc.
Ballroom dancing is "standardized" primarily for competition purposes. In this case there is an authority judging the dancers for quality of movement, musically, etc.
Bottom line the, "rules" generate more feeling and the feeling is why we dance.