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

"Why would anyone marry a brunette when blondes always have more fun?"

If you wanna be happy for the rest of your life, never make a pretty woman your wife...

Yeah, find someone as ugly as yourself and be happy together.

if you wanna be happy for the rest of your life never - Google Search

In solid state amps only a handful and in tube only a handful also they are incredibly difficult to make and unreliable due to heat generation because of the 10 percent efficiency. So most of the makers if not all stopped making them.

This statement is false. We've been making class A amps for over 45 years. Reliability isn't an issue- that's an engineering problem, not something inherent in the class of operation. They are more efficient than 10% too- that's about a country mile off as the saying goes.

"...that’s an engineering problem..."

Are class A amplifiers significantly harder to engineer, or they are about the same but only bring some of the well-known things (heat) with them simply because of class?

Also, how does efficiency of class-A amplifiers compare with other classes (ballpark figures)?