Question on strategy

[Scrapper1]

I never played the game, so while I understand the rules, I don't always grasp WHY things are done a certain way. So here's my question.

Probably 90% of the time, a team's setter starts the set in serving position 1 or position 2. I think I understand why they do this. You want a back row setter right from the first time you serve.

But sometimes the setter starts in serving position 6 (Rotation 2). Is there a specific strategy being employed in doing this? Apart from not understanding an advantage to the team in doing it this way, but (selfishly) it also makes it harder for me to track the team rotations. (Are they one ahead or one behind the other team's rotation. . .?)

So what's the advantage of starting in Rotation 2 over Rotation 1? Thanks for any insight.