I put them on some beds (I put them where the spuds were that year, so that it is another few years before Spuds see the soil again as Toms and Spuds have the same diseases).
That might be a reason for not putting them on the compost heap - presuming that your compost gets put on pretty much all your beds? but having said that much of my spent potting compost goes into the compost bin.
And some I use at the bottom of Urns and Tubs - with fresh compost on top. I mix a slow acting granular fertilizer into the old compost, and moisture retaining gel (which I don't put in the top compost because it just comes to the surface as it absorbs water and expands, so I assume does little good