This "race to the bottom" is exactly what consumers have asked for.
NK wouldn't be the fastest growing airline in the country if everyone who flew them immediately swore them off completely and actually stuck by that.
Jetblue tried to keep more pitch but people didn't want to pay for it, so now that pitch is going away.
It would be intriguing if Kayak could show you the price per cubic inch of space you'll get, that might turn some heads! (I know this is in no way practical or really doable but it would be interesting none the less)