Also, because there are still questions about whether the Iridium team have
successfully removed all proprietary code from upstream. See:
https://trisquel.info/en/forum/confirmation-iridium-libre
>(Abrowser) which Trisquel's developer maintains
That's Icecat.
Because it already has a free software browser (Abrowser) which Trisquel's
developer maintains (which includes removing suggestions of non-free add-ons,
removing DRM support, and providing a free add-on repository).
Making Iridium completely free would likely also require some work (such as
Question in title