... or bake your cake, or arrange your flowers, or DJ, etc.
As a photographer I see posts on social media like this all the time! Basically, the story goes that you don't take your own wedding photos (or hire a cheap friend/family member) because the person who's writing that post takes photos that are clearly superior to everyone else know. And they can of course do the best job. While that maybe true, it's highly unlikely that's the reason most people choose who to hire.
Here's another line of thinking.
Your wedding is a celebration of your marriage. And marriage is about unity. There's no better way to create, assure, and celebrate unity fan by building community.
The idea is not to think about "hiring vendors" to work your wedding, but rather think about "inviting members" into community with you. Find people that, through your experience with them, will help build unity in your marriage. Let the people closest to you be a part of the experience, and find people (photographer, caterer, DJ)who make your wedding a better experience for you and for those close to you.
Build your entire engagement period, wedding day, and marriage experience with this thought in mind: The better the community around us, the better the unity within us.