If you provide a service to your customers, and you fail to provide the service on a regular basis, you dont simply shrug and tell them "well thats just how it is sometimes, learn to live with it. Keep giving us money."
Every business proceeds on the expectation that the customer will actually get what they pay for. When that expectation is not met, the business does what it can to ensure it wont happen again. Or it makes amends to its customers for failing them - that's what a guarantee means.
I dont know why you're digging your heels in the sand so hard on this. This is basic customer service precepts.