I think you're looking at something that is far bigger than most MA instructors/school owners have in mind. They sell to their students - you're talking about trying to market to the general public. That's not a MA business - it's a clothing business, a supplement business, etc. Not a bad business, but not in the same niche, at all. And not what most folks are in this to do.I will just say, again, that if your idea of growing your business is just filling your student roster, you're just looking for a handful of students, just do some flyers, etc...
But that is a very limited view of your profit potential... Why would you not want to monetize your website? Even if it is only through affiliate links or ppc banners? Why not have a cool looking brand and sell workout clothing? Supplements with your logo on them? Video courses? And on & on & on... All you need is the structure, something to sell, the traffic and the leads.
That is all stuff I think every business owner should be doing in one way or another.
You do what you think is right for you and yours. Some just want a small gym, some want to grow beyond that. That's why you look at marketing.
My idea of growing a business is just different than your idea of growing a business.
But this is the digital age... confining your potential to a brick and mortar is going to a limiting factor on how much you can earn in your chosen field.
It's like asking an ice cream place why they don't have a whole clothing brand. They may have some t-shirts for regulars and/or tourists, but having a whole clothing line is just an entirely different business.
EDIT: I'll also add that trying to start a clothing brand based on a MA school sounds like a low-percentage play, unless the school is really well known, because of some celebrity (MMA fighter, etc.).