To be honest, I really don't know. I've used gcam both with and without AR services installed. It worked the same both ways as far as I could tell. Maybe it's required for something I don't use so I didn't notice, or maybe they added it in preparation for a new feature.
AR services are probably necessary for some things like games (like Pokémon GO) or maybe even something like Snapchat filters.
Disabling it won't hurt anything. Just remember you did and if something AR related doesn't work just remember to re-enable it. Or, just leave it enabled and remove its network permission. It shouldn't need access to the internet anyway.