Pi filter output stage

[P.Mouse]

In switching regulators/power supplies a Pi Filter (CLC) is mostly used on the input to prevent any noise getting back into the mains.

I actually have never seen a decent Pi filter at the output stage of a switching power supply (or even a DC-DC buck/boost converter).
Is there any reason besides costs and board space to NOT use a pi filter (CLC) at the output stage of a switching regulator?
With a decent pi filter you can easily bring the noise down by a factor 10 or more.

[AlienRelics]

Inductors were great for smoothing in tube circuits, because tube circuits were generally designed so everything was Class A, so the average power and therefore current draw was pretty much the same all the time.

That is because an inductor tends to keep current the same.

But in a digital circuit, that is a bad idea! CMOS draws relatively high current spikes whenever a state is switched, which is one of the reasons why they tend to be very noisy and require a lot of bypass capacitors. In fact, a lot of attention is given to reducing inductance.

[P.Mouse]

But I guess you can dampen the inductor, or simply use a ferrite instead?

This also would still work for analog circuits (like for opamps etc)

[David Hess]

The LC filter after the output capacitor is optional and used where lower noise is required.  The trace inductance and decoupling capacitors by themselves remove the highest frequency switching noise.  Lossy inductors like ferrite beads can be used but it may be tricky to avoid saturation.  Older designs often used a wire wound inductor over a low value shunt resistor low lower Q.

Linear Technology application note 70 briefly discusses output filters.  There is another Linear Technology application note which discusses them in detail but I am not sure which one it is.