Because using a 3rd party design you have to ask or guess what each chip does, and they might not want to tell you everything for IP reasons. When you create yo

Because using a 3rd party design you have to ask or guess what each chip does, and they might not want to tell you everything for IP reasons. When you create your own board, you know what every little chip and trace does exactly, and it's a lot easier to detect a rogue chip.