Expensive pain in the ass? as in REAL hardware processing using a chipset instead of spare IO pins on the chipset and let the processor waste time doing the job?
Yeah, you needed that on a DV camera because transferring was a real-time thing thanks to the TAPE FORMAT. You had similar sync issues back when people had to load programs from cassettes. Buffers were expensive, so the channel had to be high-bandwidth and low-latency.
It was also a hard problem to solve because the format purposefully used a LOWER COMPRESSION RATIO than was possible at the time (roughly 30 Mbits/s for DVD-quality video). This was required to reduce the overall cost of the on-board processing hardware, and took advantage of the gargantuan size of the DV tape.
So, for an isolated corner-case, the Firewire system was developed. It had enough hardware support so that systems could maintain transfer rates with minimum latency, and added a reasonable amount of cost versus going with a higher video compression ratio. It was also forward-specced for the eventual release of HDV, which required roughly 100 Mbit.
Yeah... And explain why it was and still is the standard in pro video and audio? Oh it's because USB is crap for transferring huge amount of of data.
Momentum. USB 2 had more than enough bandwidth even for HDV. The worst-case read/write speeds I have seen have been 30/20 MB/s, and that's over twice the read speed you need for HDV.
USB 3.0 requires the "pain in the ass" that yu complain about as it requires a chipset to do the processing instead of being cheap crap that requires the processor to waste cycles on it.
And it introduced all those fancy features a decade after Firewire did. NOW it's incredibly cheap to package that extra processing power for accessories, because there's all sorts of free space in modern southbridge designs (they are usually pad-limited). And it's a whole lot easier to fit a complex feature in a 32nm process than it ever was inside of a 500nm process!