Merchant of Venus question

Today I was able to unpunch, sort, and bag all of the components for Merchant of Venus (2nd ed.). I've also just read the rules for the Classic game which I intend to play first before trying FFG's standard edition. I've never played before. My question involves the movement phase, "setting speed" with the dice, and then assigning one die to "navigation." The rules imply that you can assign a die to navigation before you move and reach a navigation space, but, why would you do that? What advantage do you get by assigning a die before reaching a navigation space and trying to exit? What do you experienced players say? Thanks!

I can't think of any reason you'd do it in the "classic" rules.

Yeah, no reason you'd assign the navigation (gate) die before you get to a gate.

Thanks for the replies. I'm very much looking forward to playing it.