He says checking voice mail, with all the announcements, codes and prompts, took 10 to 15 minutes out of a day, not including the time required to call each person back.
the fixed system prompt, "I'm sorry�" followed by the mailbox owner's name, then "�is currently on the phone" followed by the mailbox owner's personal greeting, and then silence.

Your prospects are under the impression that a brand will be always available to cater to them, now for some circumstances, a few brands might not be able to serve their prospects 24/7 which is why creating a voicemail message becomes useful.
The bottom line is that a business’s situation is likely to change often and rapidly, each of which need a unique and applicable voicemail greeting to cover the circumstances and timeline. For example, callers shouldn’t reach a business-as-usual voicemail, and therefore expect a return call within the business day, if the subject they’re calling is out on vacation for two weeks. Such a lack of communication is a recipe to lose that caller’s trust and tarnish the brand’s reputation.