I wanted to be able to put my families bikes into my truck bed without having them slosh around all over the place. All the bike racks I found were quite expensive. For example, this one is $300 with shipping. Too steep for my blood thank you. I could have put the bikes on the roof but I have plans to put a roof basket on the truck with lights so that wasn't going to happen. Besides, if I wanted them on the roof I'd have to invest $800+ on it. Heck, one bike tray is $200. I'm not the Prince of Monaco. Time to get cheap.
I know lot's of people make truck bed bike racks out of PVC. Here is a great one by Louislam. I respect the idea but I just can't bring myself to putting a PVC rack in my truck. It needs to be metal. I'm old fashioned that way, now get off my lawn.