Your ideas and preconceived notions block your ability to see reality, like being blinded by your map when you're already at your destination.
I was once angry with my business partner, who signed up a hotel as a customer for our internet cafe business. I thought it was a distraction; it didn't fit our marketing plan which targetted coffee shops. That hotel made more money than the rest of our cafes. Now, it's a million-dollar business selling to hotels.
A lot of tools work well when you fill them with real information, directly gathered from outside of your own head - business plans, business model canvases, personas, selling "benefits", focusing on "beach head markets."
When you use these tools to write fiction, they become detrimental filters, preventing you from seeing the real need and real opportunities.
Even when they're right in front of you.