Nearly everybody enjoys creative writing in some aspect or another. The fact of the matter is, when compared to non-fiction writing styles, it is useless in the academic world for a grand majority of people. Public school exists, theoretically, to prepare individuals to be intelligent, capable individuals who are capable of performing necessary skills in the post high-school academic world or in the job market. Teaching students creative writing doesn't really do this. This is why creative writing is often offered as an optional course, or given as a minor part of the general curriculum. Unfortunately, there are other areas which overshadow it as far as academic importance.
There are a lot of artistic functions which are overshadowed by their "academic" counterparts for academic reasons. Orchestral band classes, sometimes coupled with jazz and marching band classes are offered, but rock band or modern pop band classes are not. Creative writing classes are often overlooked or mushed as a minor part of curriculum for non-fiction writing courses. Painting, sculpting, and drawing courses (if offered) can generally only be taken at the expense of other artistic courses, and in a preset order to provide the most marketable "graphic design" skills first. It comes down to the amount of time students spend at school, the amount of time teachers spend at school, and the amount of funding the school has for extra-academic programs. Students who are very interested in these arts will pursue them outside of school, whereas it is difficult to see students pursuing essay writing, calculus, etc. outside of school.
It would be nice, but we need to make sure students are taking the courses which better prepare them first and foremost, and the courses which they feel they are interested in, but aren't likely to use in the future, after that.