My phone shows a mirror view in the screen in selfie mode, but the recorded footage and photos are not mirrored (there’s probably a setting to mirror the actual footage, but the default is normal, right-way around video that obviously preserves things like text appearing in the footage).
But if it’s not a vlog or something, the footage is typically reversed as an attempt to evade copyright detection. I would say this is the majority reason, simply because the majority of online video is now not original.
