We do! They're way behind Eagle and KiCad, but they're a fair and growing number. Our current challenge is to keep expanding our ability to automatically detect the default gerber naming scheme so it doesn't matter which CAD package you're using. I know we've recently really nailed down the Altium variants (Designer, CircuitMaker) but I'm less sure about Upverter.

One of the downsides of accepting gerber files is that a lot of folks rename to match our suggested naming pattern to be sure the files work, so it can be tough to determine which CAD package was originally used. Plus, we still get gerbers from some rare ones like TraxMaker 2000 or Ranger 3.