Vignetting correct is virtually lossless and quite predictable. So one can easily reverse it and there is little to no possible side-effect. That is why it is on by default.
Chromatic aberration removal on the other hand involves automatic detection and then replacement of suspected aberrations by colors from adjacent pixels. No only can it cause loss of details but the process is also not reversible. That is why it is off by default.
For completeness, there is one more correction which is available on some cameras and must be off by default. That is distortion correction. This is the worse kind of correction to do automatically because it affects framing. When barrel or pincushion distortion is corrected, part of the image gets cropped and you can easily end up with the edge of something or someone clipped even if you saw in the viewfinder. In those cases it would be best to do manually some correction but not do it fully to preserve the image.
Most times you can do those corrections later in software which is the safe thing to do. One would do it in the camera to save time but at the risk of some occasional mis-corrections.