I suspect it was a combination of technical limitations and the nature of the developers. The USB 1.0 standard was finalized in 1996, seven years before PCIe 1.

I suspect it was a combination of technical limitations and the nature of the developers. The USB 1.0 standard was finalized in 1996, seven years before PCIe 1.0 (2003), and was one of the first (maybe the first?) consumer protocols to fully support automatically-enumerated hot-swappable devices. (Having worked on USB drivers a bit, I still kind of hate the protocol, though.) Keep in mind too that there is a massive difference in computing power, memory, etc. between 1996 and 2003. Similarly, I get the impression that "low-power wireless" was a herculean effort when Bluetooth was developed in ~1999. It looks like PCIe 1.0 was designed solely by Intel, which probably accounts for a lot of the coherence and editing. SATA (2003) was designed by committee.