For some people, being on the phone for 45 minutes (and what guarantee is there that you'd actually get to talk to them after 45 minutes?) during business hours is simply not an option. They would have to take time off from work, which a) might not be allowed, and b) if allowed would certainly reduce their pay.

Furthermore, there's an entire category of people for whom "talk on the phone" is not an option, period. If they wanted to cancel by the approved method, they'd not only need to take that time themselves, they'd need someone else willing to take that time with them.