I'm by no means pro-Mac, in fact I'm quite the opposite. I too, like you, have seen the writing on the wall from how Apple hands the "pro" side of things these days. Even the iPhone is aging as they struggle to keep up with fierce competition. All that aside, that still doesn't negate the fact Mac Book Pros and iMacs simply sell a lot of units and are still a predominant platform for creatives.
A vast majority of tutorials created for any piece of creative software, whether it's Maya, Houdini, After Effects, Nuke, Resolve, etc are mainly created on Macs as that's what the trainers have and prefer. If you look at trainers like DT, VCP, Gnomon, FXPHD, Lynda.. most courses are developed using Mac.
I'm basing my opinion solely on the popularity of the platform as whole in the creative community and it could be why BMD considers that an attractive customer base. Just like iOS, you have to build to where the largest number of customers are, regardless of the issues involved.
Either way, I'm looking forward to seeing what is in Fusion 8 as I'm still running through CMIVFX tuts to get back up to speed after having not touched it since maybe v5. (on the teleportation tutorial now)