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

... as already noted, because it does not always sound better. I can easily design a horrendous class-A amplifier.  Design is everything. All the practical benefits are noted as well, but i can further assure you that the cost (transformer, devices, heat sinks, etc.) of a pure class-A amp consumes resources that could be better spent on sound quality elsewhere.

I can design a horrendous class whatever amp too. That's not the point. No, design is a lot but it is not everything. There are limits of what is possible.
Orpheus10, there are great SS preamps, they are expensive and one can probably do better with tubes for the same or less but I don't know it.
Boulder, Gryphon, D'Agostino, Soulution, Accuphase etc.

Yet another fine example of a tempest in a teacup.

Hey, y'all.  Let's visit each others' homes and argue about the color selections of wall paint, furnishings, each others' shoes....

...that dumb aze Porsche vs. a nice Cadillac SUV.....with all the options...

The latter strikes me as the most blatant offering of a pointless ego toy that will NEVER see muddy roads....perhaps a deep puddle @ the mall....the bumpy RR Xing that gets 'tippy-toed' over...

Give it a break....:(

Strange noboby is complaining about weight and dimensions of class A serious equipment.
I just gave away two clones of class A Pass Labs and I'm looking for a good traditional A/B amplifier, because I'm tired of turning on two blocks each time, having double waste of space (one block on floor and the other in the rack), having to move 38kg (83lbs) for each operation on every block for cables, cleaning floors, etc. The difference in sound is evident, as well as the inconvenience.
Just my experience.

Clearly, there are lovely examples of amps of all description. That said, I still occasionally hear old low watt Levinsen and Krell class A devices which move me to tears. There is something there. Options exist at my house but a Pass XA-30.5 remains an object of my most ardent affection.