why doesnt hitfilm pro 2017 import flac and does the most recent version of hitfilm pro at least import audio flac files?
Why? Because the devs haven't added support. If that's flippant, this is primarily a user based forum (Mods are user volunteers), and we don't know why FXhome makes the decisions they do.
The current version of Pro doesn't import FLAC either.
Adobe After Effects, Premiere, Avid, and Final Cut also don't have FLAC support.
The only commercial NLEs with FLAC support are Vegas Pro (which has had it for a decade) and DaVinci Resolve (which added it last year).
You can make a feature request here.
But read this first.