Many sectors use zero hours contract workers these days. It is regarded as the most cost-effective way of meeting short-term staffing needs. Zero hour employees are not guaranteed work and are only paid for the hours they do work.
The main responsibility of corporations used to be the generation of profits at any cost. Even today, there is zero point in a business behaving responsibly if, in so-doing, it puts itself out of business or generates less profit. That's why corporate social responsibility aims to contribute to profit, rather than being a net cost.