In Collector, when attaching photos to a feature collected in the field, no GPS EXIF data is recorded in the file on both iOS and Android platforms.
It would be useful to have the geotag data in addition to the location from the feature photos are attached to. I collect many linear feautures, for example, and it is useful to know where along the line a photo was recorded. Geotagging also records the direction the camera was facing, another useful datapoint.