I would argue that the decisions of individual captains don't matter as much in a 3v3. When an ally dies in a 2v2 the remaining captain can stay and try to finish the kill, or run to regroup. On the other hand if an ally dies in a 3v3 running means certain death for the remaining ship. Even if the runner does get away and forms up with the first ally who died the length of time it will take the 3rd ally to get back in the fight is often longer than it takes for the enemy to catch you.
It is also too easy for a 3 ship combo to focus down an individual ship of a smaller formation essentially tuning a 3v2 into a 3v1 before the weaker team can turn the situation into a 2v2.
