Earlier quoted context omitted.
Blind people are the same as everyone else, but with reduced vision. So when you ask "Why don't blind people just call?" you actually need to be asking "Why don't I just call?" Blind people will have the same reasons.
If they didn't have online only deals wouldn't providing a person to talk to meet their burden of enabling that user?
If there was an online system that only worked with screen readers and the company said "sighted users can just call instead" I wouldn't use that company, and if they had the best price offering I'd be very annoyed. Making an inaccessible website is exactly the same.