16:9 was a compromise, but not in the way you think
I was always under the impression that the 16:9 ratio was a compromise chosen that was governed by the physical characteristics of the glass CRT technology of the day. 16:9 ratio TV's pre-date LCD or plasma by a relatively long timeframe. i.e. tubes with display surfaces of wider aspect ratios were simply impractical and uneconomic to manufacture.
Once established however, 16:9 became a format in it's own right, such that even in display technologies not constrained by the same considerations (i.e. early LCD video projectors of the day) 16:9 became the defacto standard for video. iirc Sony did have a 21:9 LCD projector a long time ago.
More importantly, in a convergent world, a 21:9 wide screen provides far greater width for side-by-side content, e.g. video chat or to upgrade PiP (Picture In Picture) with PaP (Picture Alongside Picture).
But unless Phillips manage to get the entire display technology industry on-board and establish 21:9 as a viable standard, driving development of content and content delivery to take advantage of it, 21:9 TV's will be largely a curiosity in the same way that Sony's 21:9 projector was.
Also note that as far as I know, "widescreen" only means 16:9 when used to describe a TV or DVD content formatted for presentation on such.
"widescreen" in movies (i.e. the actual content) refers to anything wider than Academy ratio (4:3)