My father in law ran a cattle ranch in Nevada. He always stressed the importance of being able to do any job on the ranch.
He said that no business owner should ever be in a position where an employee knew how to do things that the owner could not do. What if something happens to that person or, if for whatever reason, they move on at some point.
If their job is critical to the operation, their absence could bring the whole thing to a halt.
This is not to say that having key employees is a bad idea. Obviously, any business bigger than a one-man shop is going to need people. And some of those people are going to have skills in certain areas that are important to daily operations. But no one person should be counted on for something that has to happen in order for the work to continue.
Someone has to be available to step in. If a replacement cannot be found quickly, it might be necessary for you, as the business owner, to be able to fill in or even assume the extra workload.
It’s your business. Ultimately, it’s on you to keep it running. If you can’t do what your employees can do, you could end up in trouble.