I accomplished two firsts at the University of Miami. One, I was the first singer to major in music theory/composition.That is, I was the first theory-comp student whose declared principal instrument was voice, as opposed to the instruments almost exclusively associated with the study of music theory: piano and percussion dominate the field. After that, almost any instrument is well represented... except voice. 

 

One is not merely a music major; one must declare a principal instrument. This declaration is important (especially to the school or department of music) because studying one of the disciplines of music without having a principal instrument is like studying any art form within a vacuum of expression. If one is in music at all, one is expected to  play some instrument, and the voice is the primal instrument.

 

Singers do not usually go into theory-composition. The most likely destination for singers is applied music: the voice itself as a performing art. After that, choral studies and music education are common locales for singers. Theory, however, is considered a discipline for "real" musicians, and singers historically have a bad reputation for lacking musicianship and musicality.

 

Consider the overabundant reason high school students wind up in chorus: someone goofed up their records in the office, or as in olden times, your "IBM slip" got misplaced. Even when those students actually opt for chorus, in many prep schools, choral groups cannot match the instrumental groups for associated study of theory and sight-reading. With the exception perhaps for magnet schools that specialize in the performing arts, choral students are left in the dust when compared to bands and orchestras. The latter have more access to striving for "first chair" status, going to contests, taking music lessons, and generally accumulating a larger volume of music theory along the way.

 

The result is, a student heading on to a college level music school from a prep choral program is quite behind the prep instrumentalist in musicality and musicianship. This is one reason that singers in general do not clamor for theory and composition as do instrumentalists. I assume it is also the reason that, in the University of Miami's 40 years before I showed up, no singer had sought a degree in music theory... or to put it the other way: no would-be theorist (arranger/composer/orchestrator) had declared his/her principal instrument to be voice. This is not to say, of course, that theory students before me were not a good singers; I imagine there were many who were proficient in singing, but they had a more significant principal instrument made out of brass and/or wood. 

 

The head of the theory/composition department,