With USB3 you have 94 i/o…
For years pci has not been mandatory for audio. UAD, Apogee, RME and other high end brands will push you to them. Or even only provide them as usb device… even Thunderbolt is not needed here.
And that’s been the case for a while! My Fireface UC from 15 years ago can deal with 16 channels at 96khz at 256 sample. On PC and Mac.
Incredible products, definitely worth the premium.