Ever since Photoshop and digital photography were invented, there's been very little reason to do this.
You can take multiple frames and combine them later in Photoshop. It only takes a few seconds, and gives you much more flexibility than doing it in-camera.
In-camera, if one exposure is messed up (for any reason), the whole shot is gone. Doing it in Photoshop, you can just exclude the frame that doesn't work (or the part of the frame containing the problem, e.g. someone walking into your frame during the exposure). Also, you can make multiple versions of the same scene in Photoshop, by combining (or excluding) frames in different ways, that you can't do in-camera.
The only technical reason for doing it in-camera would be file space. Storage is cheap.