Actually they are ahead of the curve. USB 4 is coming soon and it will support TB3. Them having a product already on the market and figuring out tweaks before USB 4 happens is a big deal.
Apart from Mac people, and Music producers no one cares or uses it. TB is actually amazing. It is PCI-E interface through cable. And you can daisy-chain many things that don't need full bandwidth. I hate wasting PCI-E slots on a thing like a capture card that doesn't actually need to occupy all that potential bandwidth.
With NVME storage becoming cheep you will need those slots. Think about this ADATA SX8200 Pro 2TB is roughly the same price as Samsung 860 Evo 2TB... I mean... WTF???

So do you want to have a capture card in PCI-E slot and 4TB of SATA storage, or a capture card via TB and 4TB of NVME storage in that PCI-E slot?