Why is "Duty Roulette" a solo feature?

[Tyrial]

How is, promoting the opposite of this (just to have shorter queues?), a nice thing?

Moreover, while I read a lot of your opinions, has any of you a source for this being the official reason?

There was an official explanation somewhere, but I honestly can't be bothered to go digging for it. All you need to do is look at the way the Duty Roulette is set up to see why it is the way it is. It has nothing to do with pre-made groups and such, all it is is incentive to get people to queue up solo to fill needed roles that other groups can't seem to fill. To make this an appealing thing to do they offer a reward (increased GC seals, Myth/Philos, Gil, etc).

Honestly not sure why it's such a big deal. Do your pre-made stuff when your friends are on, use DR when you're alone.