BUT, most reception venues will only allow cakes made by professional bakeries to be served. Food and safety, and whatnot.
My aunt made my cake. She is not a professional. My venue never asked me where it came from, so I'm not sure that's true.
Your wedding cake is the centrepiece of your reception, it is in your photos for all time. It is also what you give your guests to eat, and if you want to save money, it can be used as dessert. The reason to get someone else to make it for you, is that you want to be as stressfree as possible leading up to your wedding. Making and decorating a wedding cake is not exactly stress free, because it is for such an important occasion it has to be perfect. Making the same old dessert that you have every other time is not going to cut it for your wedding, it won't be special enough.
Honestly seaweed, I don't think that the majority of brides place this much significance on their wedding cake. I think its absolutely fine if its very imporant to you, but my cake wasn't the centrepiece of my reception - because I didn't make it so. It's in a small handful of photos. Had I had no cake at all, my wedding would not have been any less significant. In fact, I only had a cake because my dad LOVES wedding fruitcake. I didn't even eat any.