Hawke is marked as Fereldan throughout DA2. It matters at the start of the game because it explains his refugee status and the desperation in going on the Expedition - people do not hire even capable Fereldans to do very much. It matters to the meta-plot because Cass suspects that Anders' plot was actually a plot that was hatched in Ferelden. And it carries throughout the Kirkwall narrative because Hawke is always cast as the Outsider.
Fereldan is also known as a backwater, and there are tensions with Orlais. Being a marcher means that you bring a whole new perspective and position to the table vis-a-vis Orlais and Ferelden - you're an outsider in both.
Ah, but DAI is going to take place in Ferelden and Orlais, a Marcher Inquisitor will be an outsider too. Both in nationality and due to the Glowing Green Hand of Salvation.
For that matter, DAO the player could be a dwarf or Dalish, outsiders in Ferelden society as well as being a Grey Warden, which puts you outside any society outside the Anderfels.
And really, I didn't see much evidence of Ferelden being particularly backwater. I find it likely propaganda; the result of Orlesian arrogance over their conquered territory.