Even on the first day of new content, people will base their decisions on the composition of the group whether to pull everything and their moms in 1 big ball. If you do a mass pull with 2 melees + a SCH, good luck to you; even a WHM's holy spam isn't going to save you, especially in the newer instances with mobs that have a much higher HP pool. However, if you have 2 BLM's, well... I think you get the point.

More to the point of why people speed run in general: People have other things to do either in game or IRL. They don't want to spend more than 30mins of their time spamming the same button sets in a dungeon. It gets repetitive and boring, especailly in dungeons that don't really require that much thinking; they aren't coil. Not to mention people who need to spam them for Poet cap/ current relic quests. I don't want to see someone be in the news for gouging their eye out over FF.