jimmysmitty, the problem is, if you're upgrading the CPU, you need a BIOS that supports both the first CPU and its upgrade. For example, if you have a Ryzen 2 and want to upgrade to a Ryzen 3, you need a BIOS that supports both processors.
And furthermore, when they ship a retail motherboard, they have no idea which CPU someone will install it in. Let's say they ship the motherboard with the BIOS supporting the Ryzen 1&2. Then what's someone with a Ryzen 3 supposed to do? Similarly, if they ship the motherboard with the BIOS supporting the Ryzen 3, then what is someone with a Ryzen 1 or 2 supposed to do?
Theoretically, a person could be upgrading from anything to anything. And if they buy a new retail motherboard, they could be installing anything. So that makes it hard. If the manufacturer says they support CPUs X, Y, and Z, then they need a BIOS that supports all those CPUs at once.