I don't, personally, but the hi-res stereo mixes are highly desirable to some.As long as you have the Quad versions who cares if the other layer is stereo or mono!
This was explained to me, in that other audiophile forum we use, when I made this exact comment.
In that case, generous folks might privately & discreetly offer to help someone in need.
That would not be me, as I agree with the above sentiment and never bothered.
As I recall, rather than "mono," the authoring mistake was a stereo channel being duplicated on both sides, leaving half the mix missing?
Never been interested enough to try to hear it on my "defective" discs.