"We don't need to update our website because we get referrals by the phone.”
I hate to break it to you but we live in 2019, the year when everyone has a small computer in their pocket at all times, so when someone refers a business to a friend everyone immediately goes to the website to check a them out. If the site is terrible then no one will want to work with you, I can't count the number of times I have gone to a site and the completely ignored a trusted referral because the page took forever to load or looked tacky or I couldn't find something.
If a customer can't find what they are looking for or they have trouble with the site then you instantly lose a potential client. You don't know the client that never called you. So you will never know how many clients you lost from your out of date website. A business might be thriving, but if they have an out of date website they might only be getting a third of the customers they should be.
People will always end up on your website. You can’t tell everyone you give your card to ‘oh no don't look at my site, we are going to update it eventually I promise’ you are effectively taking a big red button and placing in front of a child and saying "don't press that", they are going to go to your website the first chance they get. You want people who are referring you to be able to show potential clients your website. People are visual creatures, so unless your product is physical and they happen to have some of it on them your helpful referrer has nothing to show the potential customer besides your website, and let's face it if your website is not up to date we know your social media isn't either so with every new platform they try your company looks less and less valuable.
At the end of the day it's simple, imagine if a record was kept of every single time you lost a customer due to a bad website, at the end of the year you look at your reports and see that you would have brought in three times the revenue had those potential clients been able to find what they wanted on your site. How long would it take you to call up a web developer?