I'm lucky to get 2 bars and I'm in an area that gets full bars with other roms.
Sent from my VM670 using Tapatalk
Battery savings...at a cost... That is my guess. Or the bars are rescaled. Remember when the iPhone came out with artificially high reception, and they had to issue a software update to show the correct reception. Maybe aosp shows the true reception, and the other roms are lying to you because they are based on LGE's source.