Class A and AB amps often have significant output impedance due to how they are constructed, and used to be the standard. They still are the standard for HiFi audio. The other types of amps are generally pretty low impedance.
Edit: Amp types as pointed out by another commenter.
Class AB amplifiers (basically class B but with an overlap region when switching between the output devices) have very low output impedance when they feature negative feedback. Which is the standard for hi-fi audio.
I wouldn't call Class A "standard", unless you're including class AB in that? Pure class A is a bit esoteric since it's wildly inefficient compared to D or even AB.
Edit: Amp types as pointed out by another commenter.