Your website is a target for hackers. Hackers want to be able to access the private information of your business, your customers, and the general public. This information is valuable for various crimes like identity theft and credit card fraud. The only way to help reduce internet crime is to make your website more difficult to hack.
The first and most important way to prevent hacking is to ensure your website is regularly updated to the latest software. If you are hosting your own Wordpress installation then you need to ensure that you update the Wordpress version frequently. Not updating can leave your website open to vulnerabilities that allow hackers in.
It's often best explained with an analogy. Imagine you own a house, but there's a hole in the wall that allows mice to get inside to steal cheese. You can patch that hole or you can leave it unpatched. If you don't patch the hole eventually more and more mice, and eventually even squirrels and raccoons may get into your house.
Websites look similar. Here's a fake vulnerability example. Imagine your website contains a web page like "/customers". Normally you have to be logged in and this page will show all your customer's phone numbers so that you can call them. But hackers could discover that if they change it to "/customers?role=administrator" then they could get access to all your private information. Normally vulnerabilities are far far more sophisticated than this, but this may help you to understand why your website needs to stay updated.