That’s a great question!
I have used linear regulators after a switching regulator before in order to take advantage of the Power Supply Rejection Ratio (PSRR) of the linear regulators. This means it will help to effectively filter out noise due to the switching regulator.
The LM1084 has this listed as “Ripple Rejection” and spec’d at 75 dB at 120 Hz:
Really you need to look at the table to see the rejection ratio over the frequency range:
Most linear regulators are just tiny control systems, so the system has a natural “roll off” that corresponds to the frequency response of that control system. Small spikes that are not supposed to be there will be squashed by the control system.
As with any linear regulator, you’ll need to have some amount of voltage differential between in and out, so that’s important to know for designing your system. So maybe you use a switcher to go from 24V down to 7V (if it’s adjustable) where you can efficiently convert down to a lower voltage, but then you put the 7V into a 5V regulator to help “clean up” the signal; the cost of doing so is that final 2V you drop in the linear regulator, at say, 1A, would result in 2W burned on the linear regulator.
This is all less important if the 5V is going into something that will introduce more noise (digital, motors, etc). But quite important in analog!