Therapists don't need voice mail messages that demean their patients. I just called a psychotherapist colleague and listened to her voicemail greeting with the now-ubiquitous message, “If this is an emergency, hang up and call 911.” My professional voicemail will never include such a message.
Professional voicemails are important, because they’re an extension of your personal brand, reflecting what level of professionalism you offer. Use these voicemail greetings for work or personal cell phone messages for your specific needs. You can choose a voice that will best suit your business and will deliver a warm and professional voice message. Your callers don’t want to hear a cold and indifferent machine voice. The information you want to put in your voicemail should be succinct enough for your callers to get every bit of information they need. Leave the relevant information in a clear and precise manner. Professional voicemail greetings for work should be informative. The first message the customer hears should have the company’s name so they can be sure they’ve reached the right number. Be courteous and informative. This could be their first point of contact, and you want it to be enjoyable. You may also like 30 Best Wishes and Congratulations for New Business Adventures If you’re going to make your voicemail message humorous in some way, it should be tasteful and aligned to your brand. It shouldn’t get in the way of giving customers enough information when they call. Your voicemail greetings for work should be welcoming and friendly but not too informal. Customers want to feel confident that they’ve contacted a professional, that the company values their call, and they have made the right choice. So be friendly but not too nonchalant. Your voicemail greeting should be clear, concise and to-the-point. You don’t have to put your clients through a sales pitch when they are trying to just get some information.

And best of all-- you can usually set it to forward the call to your cell phone when you are away from the office, thus preventing the need to ever give out your personal cellphone number.
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.)