That's not the motherboards fault, the PCIe controller is on the CPU and needs to have corresponding I/O pinout on the socket. And even from the CPU manufacturer side, it's not artificial market segmentation. The I/O die alone on an EPYC/ThreadRipper Pro is more than double the die area of the CPU, GPU and I/O chips in a Ryzen 7 7800, and it's on a single chip which makes yields way worse. The socket and package need 1700 connections in one case and 6000 on the other. The high I/O CPU is way more expensive to manufacture, and on the lower end the prices start at ~1k for 512 GB/s of full duplex PCIe bandwidth and 12 memory channels.
