It's the same with plumbing, wiring, programing, writing, cooking, gardening, and most of the other verbs.

For the most part, everyone can do these things, but it's nice to pay someome else to do it; especially in fields where experience gives expertise and hopefully wisdom. Also, it's handy to hire a licensed practicioner in fields where government requires licensure to sell services.

Some people are really woried about making big mistakes that are expensive to clean when plumbing or wiring or lawyering. It's a legitimate thing to consider.