Recurring Theme On Specific Class Demands Per Content Because of Difficulty.

[Rentahamster]

There are many ways to beat the content, but no one knows about them because the playerbase sees how the Japanese or BG does content and sticks to that

They're not doing it that way to mimic BG, they're doing it that way because it is the easiest way to do it. No one's going to intentionally make a fight harder for themselves if they don't have to. It is objectively easier to beat Ifrit using lancers as DD. That's really the only thing at play here.