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

My new amp being built is in 3 chasses. But it is really to make it one-man portable. I specified the heaviest chassis to be 50 lbs.   So far the interconnecting cables are complete.  the transformers are in transit from Europe.

Jerry

@gs5556 You lost me at "circuit boards"...point to point is a design requirement for me.

Like these Valvet?

The only reason not to is cost. The reason to is mains isolation. The distance between them is irrelevant provided a shielded cable of suitable gauge is provided. Yes shielded as DC is easily contaminated.

If you don't have separates, and you're brave enough, open the case and with a sheet of aluminium, cut and fit shielding around the power transformer and if possible around the DC power board. Don't stop there, do all your equipment and you'll be shocked at the improvement, no matter what the purchase price.

I design power amps.

Simple: cost.  The added chassis adds a LOT of cost that could be invested in more important improvements. And it hits again raising shipping costs, also a LOT.  The advantages can be minimized through shielding of the only noisy parts - the transformers. Finally, all power amp signals are fairly large, so they are not terribly suceptible to noise compared to things like DACs and RIAA (phono) stages.  The input to a power amp is, by convention ~ 1V rmp for full output.  The input of some moving coil cartridges, by way of comparison, is 1/2 of 1/1000th V (in other words 00.5 mV). Line stage preamps fall int he middle.

That said, for a recent prototype that i constructed i did just that - mostly to make it easier to work on and experiment with tho.....but everyone seems to thinkl its cool. :-)