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

The history of audio shows that you cannot make blanket assumptions on any product based on theory: There are too many variables to make any conclusion that class A is always sounds better than class AB. The results are aways dependent on the synergy between the amp, speakers, and room.

Basically you can say, all things being equal Class A sounds better, but all things are rarely equal are they?  I can't see myself owning anything other than a Class A triode wired tube amp but my setup is optimized for that style of amp.

Yes but take away blanket assumptions and there goes 80% of site content. Take away pure unsubstantiated blather and there'd be like three of us left all reading each other.

For what it's worth, I have two Class A amps, a Reference Line Silver Signature (modded by Roger Modjeski, RIP) and a Plinius SA-103 (heavily modded by Vince Galbo Designs). Both put more than 100w into 8 ohms. I used to have Bryston 28B SST2, an AB amp that put 1000 watts into 8 ohms. I had all three amps at the same time, so I could easily compare them in my system, which includes PMC IB2i speakers (known to love Brystons). The class A amps sounded better by pretty much every parameter. The Brystons are long gone. What's more, the Plinius has a button you can press to switch the bias from AB to A. Class A sounds better, by no small margin. Again, FWIW.