Is "capable" the enemy of "great"?

In my training class today, I told them that if a “process is capable, thus meets the needs of the customer, why improve it”? My theory was, and is, that if you are “good enough”, why spend the time and money to be great. I’m still not convinced that this is not true in business, but could it not be true that “good enough” is the enemy of great?

Perhaps your process may be good enough to meet the customer’s business goals, but should that mean that it is good enough for you? I would say that the answer is no, that you should always have business goals that drive you to better and better processes, even if your current customers don’t need them. Perhaps it is only through continuing to improve your processes, you become capable of performing for customers who are more demanding than the ones that you currently have.

Therefore, does having mediocre customers or customers that are accepting of the status quo, lead truly world class companies to fail to achieve what otherwise may be possible? Should we always be looking for customers that drive us to be better than we are today instead of only doing business with the ones that can accept us as we are?