Hey, sorry I missed you. There may be one of the reasons why I can’t get to the phone: a) I’m with my girl (laugh), b) I am totally wasted and can’t remember how to use a phone, or c) I just don’t wanna talk to YOU. Leave a message.
A professional voicemail greeting is a vital component of your communication strategy. It can increase engagement with your clients, create rapport and leave a good first impression when you're currently not available to pick up the phone.

In my (US-based) experience, doctor offices & the like have a place where you can fill out if they can leave messages or not (and some even have asked detailed messages vs callback messages), so that's my perspective! And that I can set different things for different numbers. So my cell phone they can leave detailed messages on any matter, my mother's house phone is detailed from billing only and otherwise callback, her cell phone is callback only. (And they also aren't allowed to tell her anything other than billing, so even if she does call them back about anything else! That was just a measure set up when I lived with her one summer & had no cell reception at her house.)
For many businesses and professionals, your voicemail greeting is going to be the first point-of-contact for your customers. This is especially true for service businesses, who often rely on their voicemail to collect information from interested parties.