There are always exceptions to prove any case, but the reality (r e a l i t y) is that PCs are in general more easily expandable internally than Macs, be it desktop, tower, server or notebook, than Macs. For that reason, there has been less impetus for Thunderbolt on Windows and so we don't see as many options or as much uptake.
USB, Firewire, Ethernet, etc - are all very slow compared to SATA3 or PCI-e.
That doesn't make Mac bad or PC good or vice versa - it just "is".
In time, the market may change, but not yet.