Why don't higher end amplifiers come with a separate power chassis?

Seems to me the amplifier is deserving of a separate power box and all the rational to not do it doesn’t make sense. The impact on sound could be huge if done properly.

@emergingsoul Keeping the power supply as close to the output section as possible is really important. You can have some pretty heavy current moving about and best not to have voltage drops due to any distance. Sometimes though an outboard supply has to happen; when this is the case if you do it properly you have to jump through some hoops to prevent the distance from interfering with the performance of the amplifier circuit.

Frankly I don't see how marginally dripping the voltage with a tiny resistor is going to achieve anything.

It depends on the circuit and how the resistance is applied.

Naim Audio uses seperate power supplies for there amplifiers, preamplifiers, streaming devices. Many units can be fitted with two separate power supplies, one for each channel. The Supernait 3 Integrated Amplifier can also be upgraded by using their HiCap outboard power supply to power the preamp section. Naim recommends using two Naim Frame Audio Racks to separate the large power supplies on one rack and the critical circuitry of the amplifier, preamplifier and streaming devices on the other. Naim’s philosophy - separate the Brian’s from the Braun. This technique keeps any transformer hum from compromising the delicate Audio signal.

Naim do.

PS 3000 HV Power supply (ta-hifi.de)

My amp has two power supplies and a battery.