The same could be said for styling hair. Some people have the touch and others don't ( I certainly DON'T). And, I think most people know, from experience, that just because someone has a license to do hair, doesn't mean they have the touch or the eye for it.
A lot more goes into designing a home than choosing just pretty fabric or the right paint colors. Architecture & Design go hand in hand, and a good designer is well-educated to know how they work together. Just like a good stylist knows that the hair cut should work with the shape of a client's face and her hair color needs to compliment her skin tone.
I feel the classes I have taken were truly helpful and inspiring, and I can't really imagine launching a career in interior design without having had some formal training. Although, there are many great designers who probably never sat in a "design class."
But what DO interior designers learn in school? Designers learn about furniture - to recognize Rococo from Regency styles; they learn about fabric - what double rub and warp and weft mean; they learn about color - the difference between a tint, tone, and shade. They learn to draft floor plans and create renderings (like the one above). They learn to always remember the fundamentals of design - scale, proportion, and balance. They learn the steps to renovation - like before you can start a bathroom makeover, you need to know the dimensions of the toilet and how far from the wall it should be placed. Seriously. But most importantly, future designers learn from other designers who have been there and done that.
I feel my training has been a combination of informal and formal - kind of the "semi-formal" type. My "informal" education has come from the School of Home-Renovation and from design magazines, visits to museums, and studying art, film, and fashion. And from just paying attention when my husband (who isn't a contractor but could be one) speaks about following code and what size a 2x4 board really is these days. I am Certified in interior design, which is pretty much the equivalent of having an AA or trade degree - my "formal" training. But, both parts of my education in design prove to be equally valid and significant.
However, the MOST important thing I have learned in studying design is that you must KEEP LEARNING. I consider myself a life-long learner, and continue to take classes, read books, participate in webinars, etc. I think that anyone who wants to be successful as a designer, entrepreneur, or successful at whatever job you have, must devote themselves to the business of learning.
So, to that hair stylist who questioned learning to be an interior designer, I say, keep taking those cut and color classes and going to hair shows. You still have a lot to learn. We all do.