Sometimes. My biggest use is on spoken word stuff where I use an expander with a ration of under 6:1 like a noise gate but one that gently fades the track when there's silence rather than the rather jarring instant on/off like a noise gate.
There are other applications of coiurse, but that's my main one.
The hold feature on an expander makes them just like a noise gate, but without the sudden on/off. That in itself is worth using for spoken word where an on/off switch would be ANNOYING!
I don't know if you'd call it an expander, but in Reason, there's a rack extension called Selig Leveler. With it you can set the top of the leveler to just under the peak (say -6 dbFS) and then find the lowest level of the music (say -28 dbFS) and set the Curve to -22 dbFS (the difference) and it does not compress/expand the bleed/noise/breath OR the peaks. Then you just use the blend and recovery knobs to adjust wet/dry and amount of affect the effect is having. Works well to keep the dynamics from hitting ceilings on top and brings the lowest musical signal up at ratio. Like a compressor, it pumps up the volume, but like an expander, it leaves the noise underneath unboosted. You still hear the breath intakes, etc., just very quiet.