They were a sales gimmick, as were 3D TVs - I remember the hassle of getting that one into the HDMI spec for the manufacturers.
There might be a slight argument for concave PC monitors but the 'focal point' of the concave TVs was far too close to be anything more than a gimmick.
As for convex displays, you're never going to see them. The possibilities of producing an LCD or OLED that is curved in two axes simultaneously is non-existent, especially if it's just for a retro CRT look.