Folk art is art, in the most original sense of the word. Just because it is fashioned by people who may not be well known, or don't have an expensive art school education, does not make it inferior. I believe all art has its origins in folk art, including the various forms of music. Folk art is the basic root and expression of a culture.
Art is purely a matter of interpretation and perspective. Some people love modern art and others think it is worth nothing. Some love folk art and others are not impressed by it. It all boils down to personal taste and opinion. So it is hard to say from a valid or reliable point that folk art is inferior to other types of art.
Art is about conveying a message and expressing something, so how can one form of art be inferior to another? Just because one kind of art isn't considered sophisticated enough for some snobs, it's still invalid to balk at the idea of it being art.
Folk art is the kind of art that we had before art became this big industry with titles, rules, and critics. Folk art was the art that paved the way for everything else.
I don't see how one form of art can be inferior to another, and especially not folk art. It would seem to me that actually folk art represents the root of out which more finer forms of art have been derived, since ancient people began displaying self expression by embellishing their day to day tools, clothing and surroundings. What today we would consider fine art did not suddenly appear out of nowhere but out of a long history of self expression. We shouldn't denigrate folk art in favor of what we consider to be more refined pieces. Folk art continues to bring enjoyment to people to this day.