Why does a hiking app need "Always" location access?

The short answer

iOS treats an app that is not on screen as backgrounded, and a backgrounded app normally stops receiving anything, location included, unless it has been granted "Always" access. "While Using the App" is built to cut off location updates once the app is no longer the one you are looking at. A route recorded with only "While Using" granted will keep tracking while the screen is on and the app is in front, and will thin out or stop once the screen locks or you switch away — which is exactly when most people put the phone away for the rest of the walk.

The three levels, and what each one actually does

iPhone offers a location app three settings, chosen in Settings, under Privacy & Security, then Location Services, then the app itself:

• "Never" — the app gets no location data at all, at any time.
• "Ask Next Time or When I Share" / "While Using the App" — location updates flow only while the app is the one currently on screen. As soon as another app takes over, or the screen locks, iOS stops delivering new positions to it.
• "Always" — location updates keep flowing even after the app is backgrounded, so long as the app has told iOS it needs them for a running task, such as an active recording.

These are three different promises to the operating system, not three tiers of the same feature turned up or down. An app cannot upgrade itself from one to another; only you can change it, in Settings, at any time.

Why background recording specifically needs it

A phone that stayed fully awake for every app in the background, all the time, would not last a morning. iOS manages this by suspending almost everything the moment it leaves the screen, and making a narrow exception for a few declared background tasks — continuous location tracking during a walk being one of the normal ones. That exception is what lets a route keep recording with the screen off or with another app open on top, and it is gated behind "Always" specifically, because "While Using" was designed, on purpose, to stop the moment the app is no longer in view.

This is also why the prompt shows up once, early, rather than being buried in a settings screen you would only find by looking for it: the app cannot do the one thing it is for — following the whole route, not just the part where you were staring at the screen — without it.

What "Always" does and does not change

• It does not mean the app is recording constantly, in the background, whether or not you asked it to. It means that if the app is in the middle of a recording you started, that recording is allowed to keep going after you stop looking at the screen.
• It does not remove the visible cues iOS shows when an app is actively using location — the indicator in the status bar, and the periodic reminder iOS itself shows after an app has used background location a number of times, asking whether to keep allowing it, downgrade it, or stop.
• It does not lock you in. The permission can be changed back to "While Using" or "Never" at any point in Settings, and doing so takes effect immediately, no reinstall needed.
• It is a separate setting from Precise Location, which controls how exact the coordinates are rather than when they arrive. Turning Precise Location off while leaving "Always" on trades accuracy for the same always-available behaviour, not the other way round.

Things that trip people up

• Granting "While Using the App" and finding a route ends early, or has a long gap — the recording lost location updates the moment the screen locked, which is "While Using" behaving exactly as designed rather than a bug.
• Tapping "Keep Only While Using" on the reminder iOS shows partway through a long recording, without meaning to change anything — that reminder exists precisely to catch this choice, and answering it downgrades background access from then on.
• Assuming "Always" means the app is watching location outside of a recording — the setting only decides whether updates are allowed to keep flowing while backgrounded; what the app does with that allowance during an active recording is separate.
• Worrying that granting "Always" is unusual or excessive for this kind of app — it is the standard iOS mechanism every route-recording app relies on, not a special or unusual request from any one of them.

Where TrailCam fits in

TrailCam keeps recording a route while the screen is off or you are in another app, which is the entire point of starting a recording and putting the phone away rather than holding it out in front of you for the whole walk. That only keeps working with "Always" location access granted; with "While Using" only, the route will stop following you the moment you stop looking at it. The app is free to download, and this permission choice is asked once, early, rather than hidden somewhere you would need to go looking for it.