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

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.

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

Exactly.  I own four Class A amps so obviously like what they offer (aside from the heat and the electric bill), but horses for courses - some Class AB amps sound better in some systems. Generalizations like the original posts are meant to stir fuss, not logical response.

I use a Class AB tube amp in my main system as a matter of fact, and I prefer it with those speakers to the 100 lb. + Class A monos I used to use. OTOH I use a stereo Class A amp with some electrostatics and it is a great match.  YMMV