General
I think the writers have pushed the WoL's fondness and talent for associating with beast tribes to draw attention to that being a big part of the story of FFXIV--empathy and leaving the familiar city are prerequisites to being a hero.
The people in the societies that send you out to do the work of interacting with them think they know more about the situation in the world, when really, the beast tribe quests are some of the most endearing and human in the game because they focus on reconciling the past and the future--rebuilding from the ground up in a sustainable image that honors their heritage (in the Moogle and Qitari questlines, that involves interpretation of the past), forces them to go to war for their beliefs and culture (the Vath/Nonmind stuff versus the Hivemind), or requires them to build their own traditions to avoid stagnation and basically extinction (Namazu). The sustainable part comes largely from the alliances with other beast tribes (I have only done the Heavensward allied beast tribe stuff but I assume it is similar for the others).
I think the divide between the cities and the beast tribes would be a lot bigger if we weren't there to befriend them, or they might even be extinct. I like to think that they had more freedom to build out on this idea on the First because it would be hard to go back on the Source and show how society has changed in every major hub. At least until we got the untempering and alliance quests where the leaders now are understanding that allying with beast tribes is kind of a virtuous duty and a true reconciliation of past injustices and not just something to be done out of pity or necessity.
I think the writers are saying a lot about the sociological implications in the overall story over and over again and on these different levels. Maybe there are better scenes that illustrate it (Stormblood maybe?) but I think the Ladder scene is amazing and you can apply it to humanity to understand how the mental gymnastics of "beast tribes" came about. It is also central to the character of Emet-Selch.