FireWire actually predates USB, and was certainly seen as a competitor during the design process for USB. It was originally drawn up as a general-purpose serial

FireWire actually predates USB, and was certainly seen as a competitor during the design process for USB. It was originally drawn up as a general-purpose serial bus, but with a particular eye at replacing external SCSI interfaces. Certainly it's designed to interface with all sorts of professional equipment, but even in this space that particular decision is a poor one because of the universality of 5V components. Early FireWire-equipped laptops varied wildly in actual voltage delivery capabilities, and even Apple's generally capped out at around 9V, and the standard is extremely awkward and expensive to implement on the device side for many classes of devices. The main issue is that devices have to be capable of handling unregulated voltage between 8V-30V. For high-end professional equipment this is obnoxious and expensive, but manageable, but it's a complete nonstarter for nearly all other equipment, and that meant that even as the price of implementing FireWire signaling went down, it couldn't expand into a bunch of spaces it was perfectly capable of working in (including lower-end versions of said professional equipment). Even including an optional 5V power pin would have improved this situation, and could have put FireWire in a similar situation to Thunderbolt 3 now, capable of functioning with both high-end professional equipment and ordinary consumer devices.