Here is a discussion of this question by professional philosophers Edward Feser and William Vallicella. It looks like the link to the article by Keith Burgess-Jackson that started the debate is dead.
I would add another reason -- professionals dislike nonspecialists, particularly those of the "interdisciplinary" type. In this respect Rand reminds me of her fellow Russian Jew Immanuel Velikovsky. Velikovsky was a psychiatrist who had the audacity to write about mythology, ancient history, astronomy and other stuff.