Apple only has 7% market share in the mobile market yet they capture 77% of the industries profits. Clearly they are targeting the right 7% of their market.
Are you targeting the right 7% of your market?
Sure you can sell to anyone. You can build your business model around selling to anyone in your market. But are these customers the ones who really generate the profits and is your business built to ensure you capture the right profit from the right customer.
I think this comes down to the ability to say no. It comes down to the ability to clearly define what you are NOT good at and what you are NOT going to do.
And a good place to start with finding your 7% is start by defining who the other 93% are.