Being convincing is hard.
People (including you and I) are creatures of habit. Getting them to change their ways is deceptively complex.
The only thing harder than convincing one person?
Convincing a crowd of people, each with different opinions, experiences, fears, desires, budgets, hopes, and doubts.
So, in the beginning, sell to one kind of person. The narrower, the better (as long as he or she actually exists).
This creates faster feedback, makes your first few sales easier, and sets the stage for you to build out your pipeline.