The goal is generally "the consumer can't muck with it" and "DC protect on the speakers".
When you decide to complicate it a bit on an amp I built, stuff gets messy. I wanted to fuse each leg of the power supply. (4 x 50 Vdc@ 3A), the 120 V mains @ 3A and the speaker at 3 A (AGX fuse). The protection supply is fused off the mains,
If I loose any power rail, I loose all of the rails and I loose a metal oxide resistor. My "protect" isn't "consumer grade", but it works. I revered the NPN and PNP transistors and only lost the resistor. It includes exponential ramping of the audio and slow turn on because of 50,000 uF of capacitance and super fast turn off.