Alt's why?

[Meoah]

Make 6 alts, put them in 1 FC, put your main character's chocobo in the stable, train your chocobo 7 times an hour.
This is what my friend does with his alts. I don't really know what else.

You cannot do this. You get one feed for the chocobo's owner and one feed from any other character. These two may have independent cooldowns, but there are only two.

And to answer the OP, for hardcore raiders, they use alts to clear current content multiple times for loot lockouts and/or tomestone lockout.