Time I spend IRL watching a caravan cross the wilderness is time not spent watching my outpost bloom into a fortress.
But, I don't see the point of what you're saying. It's not like you would just watch the caravan move from A to B, you would be given messages like "Your caravan is crossing through the Forests of Aching. This forest reeks of death and vile torture. You see a blah blah blah". The journey could happen off-screen. Eventually, there would be a situation when you have to cross a river or fight a bear Jeremiah Johnson style or other such wild traveller things, or maybe an ambush or whatever. One of your party could become sick and you have to hunt for medicine for them, who knows. If you don't want it, you'd have a choice because it's an optional feature, just... don't choose to follow the journey. It's not like you have to. The fact that it's optional means that there's no point in complaining about it using up your time.
I missed the optional part.
Now let's get into better detail. IIRC, Toady said that the player is supposed to represent the leadership of the fortress or somesuch. What could the player, in that position, do to affect the caravan or even know about it?
That contradicts with what Toady has said about his ambition (as far as I know) to seamlessly integrate adventure mode and fortress mode together. I would also like to hear exactly what he said about what the player represents, because that's the first I've ever heard about that.
I assume that, as an adventurer, you'll be able to lead an expedition to a new fortress and issue orders from there. And I sadly can't remember the exact link, but I'm 90% sure it was some FotF thread reply.
It is also quite simple, if what you say is the situation. The leadership of the people taking the journey to build your fortress are the same as the leadership of the people who run your fortress - quite literally so, considering the expedition leader of the caravan is the same guy as the expedition leader of your fort.
Oh, I thought we were talking about caravans being sent to our fortress.