[Arran]

There is also the fact that larger value mylar/polyester film caps like 1 to 4 uf at 630 volts are really not that expensive, more expensive then an equivalent electrolytic but still cheaper then the average replacement type #80 tube.
In the older AC sets it's the field coil and filter chokes in the power supply that take out most of the ripple, at the time there were no high value filter capacitors available at a reasonable cost so they used inductive reactance for filtering rather then capacitance. After Mr. Mershon came out with his wet electrolytic capacitors it became easier and less expensive to use large value capacitors to filter out ripple rather then inductors.
Regards
Arran