Too many damn interconnect interfaces in too short a time.
1995 Firewire 400
1996 USB 1
2000 USB 2, USB Mini-A, USB Mini-B, USB Micro-B
2000 Firewire 800
2008 USB 3
2008 Firewire “declared dead” by Steve Jobs
2011 Thunderbolt 1
2013 USB 3.1
2013 Thunderbolt 2
2014 USB-C connector rises from the dead and joins all of the above USB connectors
2015 Thunderbolt 3 (adopts USB-C connector, too)
2017 USB 3.2
2019 USB 4
I purchased—with reservations—a pair of Thunderbolt 2 interfaces this Summer from Presonus. The interfaces were a good fit for my plans, but immediately necessitated a Thunderbolt 2-to-Thunderbolt 3 converter dongle thing, because Macs have shipped with Thunderbolt 3 for the last four (4) years. Why is Presonus still releasing brand new Thunderbolt 2 interfaces? Probably because the licensing and approval process for Thunderbolt 3 remains ridiculously expensive and time-consuming. (You may note that Thunderbolt 3 has been “current” for four years, but actual Thunderbolt 3 devices have been slow to arrive, remain fairly rare, and tend to cost $$$$.)