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.
Most people I know prefer to use an online system to avoid talking to people especially if there's a complex process or lots of information to enter. Blind people feel the same way. A phone based option is not "offering the same service" to blind people.
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.