There is a difference in terminology between an update and an upgrade here.
Whatever Android version you’re on, an update will update this same Android version with bug fixes, security patches, perhaps new features or feature changes etc. … the updates are identified with the date when they were built.
Upgrade in this context means to upgrade the major Android version you currently use to the next major Android version … for example from Android 9 to Android 10.
This is not trivial, it involves much more than a regular update involves.
You should get a notification from the system that an update is pending.
Else you can have a look in the updater in the Settings, currently at Settings - System updates, but the place in the Settings and the name can be subject to change.
As currently the OTA updater is only able to do updates and isn’t able to do upgrades, there currently is no confusion about what’s on offer there.
To make sure an update should be there (in case the system doesn’t offer it to you for some unknown reason), you can have a look at the available downloads at https://images.ecloud.global/dev/FP3/ for the “dev” release channel, or https://images.ecloud.global/stable/FP3/ for the “stable” release channel … if you are on Android 10 already.
If you are still on Android 9, then the list of releases should be the next best indication … https://gitlab.e.foundation/e/os/releases/-/releases. Keep in mind that “stable” updates get released several days later compared to “dev” updates (so the “dev” users can test an update a bit more before the “stable” users get it).
You can find out everything about the Android and /e/ version you currently use in Settings - About phone - Android version - /e/ version.
This currently tells me I’m using 0.17-q-20210529117214-dev-FP3.
This in turn tells me I’m using the update of /e/ version 0.17, Android 10 (“q”), built on May 29, 2021 (“20210529”), on the “dev” release channel, on the FP3 device (a Fairphone 3 or Fairphone 3+, they get the same OS builds).
Regular updates don’t wipe your data.
At least they are not intended to do this, but it’s software … I make a backup of everything important to me before every update just in case
.
Currently the data wipe is necessary when following the manual process for doing the upgrade from Android 9 to Android 10 on the Fairphone 3/3+.
As for why … I don’t know, I’m not a developer.
Conceptually it takes one possible source of trouble out of the process, but I can’t imagine this being the technical reason behind it.
And it’s dependent on the device a bit. The brave of heart could try to upgrade their Fairphone 2 without the wipe of user data. I tried that myself with my Fairphone 2 actually, and it worked, but this doesn’t apply to the Fairphone 3, it’s a very different device.