It is one thing to have a working application. But how about infrastructure? Many thought cloud could make life easier for infrastructure people. It just made life even harder. If things go wrong (chaos happens), there can be very minimal we can do to control. One thing we can do is try to plan for chaos.
Azure Chaos Studio just allows you to plan and test your infrastructure and prepare to be ready for any unexpected situations. It is not just a signal based simulation. It makes infrastructure fail for real. This makes the worst possible scenarios testable.