A big benefit of doing a job yourself and not always relying on delegation (of even the stuff you don't like doing) is that you learn so much about all aspects of your business and the people you will eventually hire to replace you.
CEOs like Joe DePinto of 7-eleven works the front line here with his employees. He works a graveyard shift, in this video. But in the whole episode he spent time doing deliveries on a truck, in the factory making donuts, and trying to sell coffee at the busiest store in their chain.
He learned a great deal about what makes his stores tick. It's not the coffee for example that people keep coming back for, it's one of the store employees who everyone loves like a mother.
Or in this clip he learns that folks working at the stores feel they aren't really part of 7-eleven as a whole company and can't advance anywhere. He also learns that 7-eleven's food donation program is off the rails and needs fixing.
Over and over again he learns great stuff each place he works with the people doing jobs he obviously is always delegating.
I even get the benefit of this working in a small business of just a few people. A couple weeks ago Javan was out. Javan normally handles most of the support of the in house installations we do of our prediction market software. So I had to handle support for this, and it's just eye opening at how much work this is for him as well as where some pitfalls exist in the installation.
We get too accustomed to wanting to hire other people to do things for us. And usually that means separating ourselves from doing the jobs that are the most customer facing. Be very careful with your desire to delegate everything. The lessons you can learn doing it yourself are tremendous.
Also, I highly recommend watching Undercover Boss.