You should definitely learn to sharpen your own knives. Home cooks can get by having their knives sharpened only a couple of times a year. When you’re cooking for a living, it’s a whole nother story. It will vary from kitchen to kitchen and station to station, but it’s common to need to sharpen your most used knives on a weekly basis or even more. That would be a lot of money and a lot of time without your knives. Plus, many “professional” sharpeners use aggressive grinding wheels. These are great because they’re fast, but they also take away a lot of metal and shouldn’t be used on a regular basis.