Because this isn't a top-of-the-line phone. It's an experiment by Purism bringing Linux and the smartphone world closer together.
I mean sure? But on the other hand it still costs 650$ so if they'd charge me double for the privacy, it should be comparable to at least 300$ which is not
I think the problem is that 802.11ac requires a non-free software blob?
It supports 802.11n, for which a non-blob solution is available.