First off, you might ask what is IVR? I know I used to.
Well, IVR stands for "Interactive voice response".
You know when you phone a company and it says "Press 1 for sales, 2 for marketing, 3 for Dave"? That's an IVR system. Often the menus are complex and can have hundreds of options across the platform. An invisible guide telling you where you are and where you can go.
The interactive part is your finger (or sometimes you speaking answers to questions), the voice response is a voice instructing and responding to your action.

Photo by Pavan Trikutam on Unsplash
But why do companies use them? Well, the benefits are numerous. Therefore, I'll use numbers.
They can reduce costs and save time. I remember working somewhere (not that many years ago) that had a huge switchboard in reception. One person would answer all incoming calls, all day, every day and route them to the required department or person. With an IVR system, that job no longer exists and all the time trying to speak to someone is put on the customer's side.
Despite making the caller do all the work to get to their destination, it improves customer service. Once the caller has made their selections, they arrive at precisely who they need to talk to. And because they've chosen a specific path to get there, the call handler is prepared. Passing from person to person and from department to department drops significantly with an IVR system. Happy customers! (Unless it's a complaint).
Call handling is more efficient. Because the call should be getting to the right person first time, every time, the right member of staff with the right skills is immediately on hand to deal with the customers request.
It can create a good first impression. A poor menu system or badly recorded messages can ruin your customers experience before getting to speak to someone. With a well thought out journey and well scripted messages, you can impress your caller right off the bat.
It makes the company look bigger than it is. Perhaps not a desire for every business to seem huge, but a company of any size could install such a system and direct calls to its staff. I could have one. Please press 1 for explainer voiceovers, 2 for commercial voiceovers, or 3 for IVR (on topic!) How good would that be? I'm tempted now. But in all seriousness, you could have 2 staff members - one sales guy, and one office manager and you could frame that as Press 1 for sales, 2 for all other enquiries. Or something.
It improves connections with the customer. Because you can customize every single message, you can really dial in (great pun there for phone fans) to your customers needs and expectations. Give them a personal experience. If you hire a professional voice artist for your IVR, the customer will stay engaged (another great pun) longer, and feel like you care about every detail of your business.
You can automate support. Depending on what your company offers, you can give assistance via IVR messages. If you're having problems with your PC, press 1. BEEP. Ok, you're having problems with your PC. Have you tried turning off and on again? Did that work? Press 1 for yes, or press 2 for yes, because that ALWAYS works. Again, this sort of thing can cut down on real life conversations and perhaps have an out of hours (unmanned) support system.
All these sound great, but like everything, if it's not done right, it can cause more harm than good. Statistics shown in an article by the Association for Psychological Science suggest a first impression is formed within 1/10th of a second - and that's when seeing someone's face. So imagine how much harder it's going to be to impress someone over the phone!
Aaand of course, with no subtlety whatsoever, here's my IVR reel.