Why would anyone want class AB amp when class A always sounds better ?

From Nelson Pass...

WHY CLASS A?

Class A operation is integral to the performance in this case, and it is worthwhile to explore why. The primary virtue of class A lies in the smooth characteristics of its operating parameters. The gain transistors are operated in their linear region only, where the distortions are limited to smooth, simple forms, unlike the abrupt distortions created when the transistors in class B output stages switch on and off."

https://www.passdiy.com/project/amplifiers/the-pass-a-40-power-amplifierhttp://

I've built a couple of his DIY Class A projects. They are exceptionally good sounding amps. Why not class A? Cost (especially cost/watt ratio), Heat and nothing else unless you're a greenie. In that case, power consumption.

There is a REAL difference in the functionality of a class A vs anything that has to "turn off" one transistor and "turn on" another one at every wave form. Just considering that it is between difficult to impossible to match those components and operate them outside of their linear reigons. Then you get into negative feedback loops to correct the crossover wave distortion, adding additional complications and additional distortion opportunities. My best example is I've owned a high-end Oddyssey amp that had a billion components in it and costs a ton. My DIY F5 Pass/First Watt amp absolutely blows it out of the water, sound-wise. There are compromises, but I sincerely believe the difference between the functionality of Class A vs class B circuit is obvious and significant.  

Broadly speaking, there are often a lot of other design variables between two SS amps beyond just the bias level of the transistors.  A lot of the high end Class A amps are designed to have very little feedback, which enhances the high linear accuracy of Class A, but often at the expense of slightly higher noise and lower damping factors.  That tends to create a certain sound which I personally feel is a bit closer to the typical tube sound.  On the flip side, it is more common for the Class AB amp designers to use some amount of local and global feedback, which "can" marginally impact the linearity, while reducing noise and increasing the damping factors and tightening the bass.  In my experience, it is very hard to generalize that Class A sounds better than Class AB since there are a bunch of other design factors that have to be considered.  The typical Class A amp may sound different than the typical Class AB amp, but it's not always better...

You don't always get what you want

but if you spend your dime

you just might find

you get what you need

Seems to me that whichever one is designed the best will sound better, be it A, A/B, or D - those letters do not specify qualitylll 

Class A sound better?  No, lots of factors to consider.  You have first of all assumed Class A sounds better.  Not always true.