If you ask 10 CEOs to tell you what marketing is, you’ll probably get 10 completely different answers. And get this. If you ask their marketing veeps the same question, you’ll get the same result.

Marketing defies definition. It confuses everyone, even those who do it for a living. I know that because that was my job in a former life, and I’m the first one to admit that I never considered myself an expert. Besides, my brethren could never agree on what their job titles meant. They were all over the map.

As I explain in my new book, Real Leaders Don’t Follow: Being Extraordinary in the Age of the Entrepreneur, marketing has always had a perception problem. It’s truly ironic that the field responsible for branding has a brand identity that’s about as unambiguous as Facebook’s 58 gender options.

And yet we live in a commercial world where consumers and businesses make buy decisions based to a large extent on a field that nobody seems to understand very well, not even those who make big bucks doing it. Don’t you find that just a little bit unsettling?

Now you know why I quit marketing. I was tired of explaining to every CEO, board, and management team what marketing is and why it’s so important to the success of the company. I felt like Sisyphus, the sinner condemned to roll a boulder uphill, only to watch it roll back down, again and again, for eternity. I always wondered what I’d done so terribly wrong in a prior life to deserve that.

Related: How and Why You Need to Make Your Own Luck

If you find marketing to be somewhat elusive, don’t feel too badly; you’re in good company. And while I intend for this to be instructive, not critical, there’s a very good chance that your company’s marketing sucks. Here’s why:

You have no idea what it is.

In his seminal book, Marketing High Technology, legendary VC and former Intel executive Bill Davidow said, “Marketing must invent complete products and drive them to commanding positions in defensible market segments.” I couldn’t agree more. And anyone who finds that confusing should not be running marketing.

It’s so easy to fake.

As VC David Hornik of August Capital says, “VCs like to think that they are marketing geniuses. We really do.” He goes on to say that they meddle in the marketing of their portfolio companies because “we can fake it far more convincingly than in other areas …” As I always say, marketing is like sex; everyone thinks they’re good at it.

You’re a follower of _____ (fill in the blank).

Marketing may be as much art as science, but it’s still a complex and nuanced discipline that takes a great deal of experience to develop some level of understanding or expertise. I don’t care if you’re into Purple Cows or The Brand Called You, popular fad-like notions won’t get you there.

You’ve lost sight of the big picture.

In some ways, growth hacking is no different from traditional marketing, and I mean that in a good way. That said, I see a lot of businesses chasing lots of small opportunities or incremental growth improvements with no overarching vision, strategy, or customer value proposition. That, in my opinion, is a recipe for disaster.

It’s built on flawed assumptions.

Most product strategies and marketing campaigns are built on assumptions that nobody ever attempts to verify because their inventors think they have all the answers. The problem is they don’t know what they don’t know. Never mind what customers say and do. What do they know?

Related: 11 Qualities Our Next President Must Have

You have an MBA.

MBAs may be good for something, but marketing is not it. I’m not saying marketing can’t be taught, it’s just that, in my experience, it’s better learned on the job in the real world. Davidow, Theodore Levitt, Regis McKenna – none of these innovators who literally wrote the book on marketing had MBAs. Maybe there’s a good reason for that.

You’re not measuring the results.

Show me a marketing program and I’ll show you beaucoup bucks spent on a mostly “shoot from the hip” approach that lacks sufficient metrics to determine if it’s effective or not. If you don’t measure it, how do you know if it’s delivering a return on investment?

You’re a marketer.

One of the reasons for marketing’s perception problem is that senior-level talent is hard to find and few execs have the ability to articulate the importance of the function. And since CEOs tend to be a pretty cynical bunch, marketing has, to a great extent, been marginalized in the business world. Sad but true.

Marketing is an enigma. It’s both art and science, creative and analytical, intuitive and logical, amorphous and tangible. It’s two sides of the same coin. That’s probably why it mystifies most. And yet, marketing is, without a doubt, among the most critical functions in every company.

That may be a perplexing paradox, but companies that somehow manage to unravel the mysteries of marketing have a far better chance of making it than those that don’t.

Related: Hubris Kills Businesses. Humility Saves Them.