Greed is a bad motivator to startup. A high profit margin is usually the last thing a customer wants.
You're confusing high-profit margin with high-profit. A company can be high-profit without a high-margin (i.e Supermarkets) or it can be high-margin without high-profits (many fashion labels). Greed is a motivator for high-profits, not necessarily high-margins.
Every corporation should be in the business to maximize profits. A high profit margin should normally relate to a higher price which will lead to a less optimal acquisition and retention of customers. A larger customer base provides stability for sustainable growth.