Because Lexus wants to make sure that the original high quality bypass valve stays when you replace the cartridge filter. The bypass valve opens in case the filter becomes clogged which could cause oil starvation and resulting engine damage. When you use a typical canister oil filter as this modification will allow, you are depending on the built-in bypass valve inside the canister of the oil filter which may or may not be equal to OEM quality.Excellent video! This is a great idea. Why would Lexus use the open element filters in the first place?