Imagine eating an entire bowl of salt.
People should only be doing this because they enjoy doing it, simple as that, you do it because you're a fan, you really love the series, and its fun.
They shouldn't do it for money, they shouldn't do it for praise, they shouldn't do it for pride.
Small groups realize this when they start, but after they do it for years and get too big it becomes less fun and starts feeling like work. At that point they should stop and let new blood take over.
Instead they keep going due to pride, get more bitter, get more paranoid, start expecting things from other people as a form of compensation for their burden, expect special treatment from the site, lash out when they don't get their way. Instead of caring about getting series they like translated they care more about how many members their group has, how many series they "control", how popular their series are, how they rank in comparison to other teams.
Their attitude turns from "I really love this series and want to share it with others" to "i'd rather see the series burn than see another group work on it".
If someone is sitting on a backlog of dozens of chapters its reasonable for a real fan to want to do them rather than wait 3 years (and the original team would almost certainly quit in that time-frame).
This isn't an assembly line or a Scanlation sweatshop. Teams don't need to collaborate to achieve the most efficient possible timing or negotiate for rights over a series, suggestion they should alternate 50/50 somehow is just greed on the fans part.
You should work on what you want because it's fun, if it isn't fun then please don't do it and don't discourage others.