Why would you waste time translating something that's being translated, when you can translate something that has no translation? This isn't for profit, competition brings nothing here as there isn't anything to compete for. All there is is wasted effort, people angry and scummy behaviour
Says you as if you don't know how many trash MTL there are floating around our community. Sometimes there are well intended TL teams that just are not up to scrutiny (even compared to a MTL) and have no real incentive to get better because of the whole "one team per title" unofficial rule.
Also if it doesn't matter why care that there are other teams translating the title anyway? You know very well why those groups care about this: Because they are looking for profit and having other team translating risks getting traffic from them.
Off course many groups do it only for operational costs but some go so far that they are charging per fraction of chapter with the treat of either you pay or wait months to have access to it, some titles they never release without paying for the chapter (not all only some).
Having multiple TL teams in one title also makes less probable that it just stops because the team gave up or moved on to some other title (with that being the main reason to be honest, I lost a lot of good stories because the team gave them up or disbanded).