Photos taken within the AllTrails app and saved to the photo roll will be saved without lat/long EXIF info because of an Apple restriction built into iOS. Try taking a pic inside Instagram (for example) - no lat/long will be saved in EXIF. However, we associate the lat/long of the phone at the time the photo is taken as part of the AllTrails recording file, and so when the photo is synced back to AllTrails, you will see a lat/long for it.
Photos taken outside the AllTrails app will have normal EXIF data, which will be read when you add the photo to a recording on your phone or upload the photo to https://www.alltrails.com on the web. Photos taken inside the AllTrails app, and then uploaded on the website will NOT have lat/long info because the files do not have EXIF data, and they are not associated with the info from the recoding.
NOTE: When adding photos that were taken outside the AllTrails app to the website or app, the photos must be in JPEG format in order to contain lat/long data.