It was "dropped" in that it's been years since you could connect a FireWire device directly to a Mac without an adapter. If we look at all the complaints about how the entire MacBook line lacks USB-A/mDP/Ethernet ports apparently people find that significant.
Yeah I get that, but in doesn't work in the same line of thinking as 3D touch, with no real alternative or successor, because it wasn't picked up. They tried 3D touch. (unfortunately for me, because I liked it, it failed)
They "tried" Firewire and it worked, and "upgraded" it with Thunderbolt 1, 2 and now 3, but it still works and is actively supported, both by Apple branded hardware and software. So it's not really dropped. Just not in plain sight.
It makes no sense anyway, because to make a one-size-fits all MacBook according to MacRumors, they'd have to include: Ethernet, Firewire, USB-A, USB-C, VGA, DVI, HDMI, DisplayPort (fullsized), MiniDisplayPort, SD Card reader.
All of which are inferior to Thunderbolt3 ports they include now, all of which get updated with years, and all of which a single Thunderbolt3 port can replace - and even support newer versions of them. They actually pulled the one-size-fits-all off with these ports if you ask me.