Competition
Lots of other companies provide the same product or service that your company does. Many of them have been doing it longer than you. Many of them have more extensive resources than you: More people. More money. More customers. More clout.
This keeps a lot of businesses (and people) from stretching. It’s intimidating to survey the landscape and see a wall of giants. You have a hard time imagining how your business could possibly compete.
Marketing is the great equalizer for underdog businesses. You may not be able to build a bigger building or hire more people, but nothing is stopping you from dominating the space between your customers’ ears.
The trick is learning to see new opportunities within established markets. You can’t own the hill that your competitor does but chances are likely that you can build a new hill that is yours alone.