1. I think the number one reason is redundancy. Don't you want your wedding to be unique? Pinterest is a fabulous place to gather initial ideas, but can you take it to the next level so Pinterest lovers are pinning YOUR wedding photos? A wedding planner and event designer can help you recreate and elaborate on your design ideas. 
2. It’s probably more expensive than you think. When’s the last time you ventured into the craft store to buy, I don’t know, scrapbook supplies or paint? That stuff isn’t cheap. Not at all. And when you start trying to arrange your own flowers (which may or may not be in season), find the 20 vases that you need, buy the satin ribbons, rent your own linens... etc. You get it. On top of the crafting being expensive, most of these stunning weddings you are seeing are super high dollar affairs, so you have to be realistic about your budget and a planner can help you achieve your look within your budget. We are THAT good. 
3. It doesn’t set its brilliant ideas up on the tables, nor does it clean those ideas up. Lauren says "So the best part of my wedding was the part when it was over, it was over. My family took the flower arrangements and we were outta there. My family and friends weren’t stuck cleaning up the room. My ah-mazing planner took care of it all. She coordinated with the vendors before the wedding, so that the only thing I had to do was show up. Pinterest does not take care of this." And you know who her wedding planner was right--yep, you guessed it! Yours truly! :) But seriously folks, if you really knew how much day of running around, coordinating and planning that it takes to get your day up and running smoothly, remain smooth and then clean up, you would be amazed. There was one wedding that had so much set up and clean up that we arrived around 8am and didn't leave until 4am. Are you prepared to put your hair and makeup on the back-burner while you oversee and aid in the installation of flowers or run back through your sparklers to pack up the guest book, gifts and strip tables of linens? NO, and you shouldn't have to, nor should your family and friends have to. They too are there to enjoy your day. 
4. Too much of a good thing, can look like too much. There are a ton of beautiful ideas on Pinterest. A TON. And in my mind, requires a great deal of editing. You want to have balance. You don’t want your wedding to look like a Pinterest board. 
5. Once you’re married you are gonna be stuck with a ton of junk. Congrats, you’re married. Now you 12-18 giant vases and 80 votive holders that you have to store in your house. Sure you can try to get some cash back on craigslist, but don’t expect to get all of your money back. And if are like Lauren, after your wedding you move into a 450 square foot apartment, you definitely WILL NOT have the room for those. Sometimes your planner or florist might be willing to buy some of your items if craigslist isn't an option, but keep in mind that trends change and therefore a lot of what you used for your wedding might not be "in" next year. Therefore, there might be very few items they will want/need. What will you do with them now? Trust me, storing them in your cabinets and garage only upset your dear hubby each time he goes to find something and knocks over a vase. 
6. No offense, but it might look a hot mess. So have you ever seen a craft project and thought... that looks like... a craft project??? Weellllllll, is your wedding day really the day to summon up your inner Martha Stewart? Isn’t it best to leave this to a professional? I don’t know about you, but I sure think so! And I don’t say this because the blog is called “The Savannah Wedding Planner,” I say it because crafts are usually fun in the beginning, but can very quickly become a flipping disaster. And when you decide to emboss 300 place cards because you saw it on Pinterest or whatever else you think would be “so super cute” after a few hours you will be over it. I swear. 
7. 99% ( a number we completely made up) of the cute wedding photos on Pinterest are of weddings that most definitely had a wedding planner. Our numbers may be off, but I assure you all of these complicated and stunning set ups with curtains and chandeliers and lanterns hanging from trees, tables with giant flower arrangements and 20 different linens and adorable menus... these were NOT diy weddings.