I mean sure, they could add more rewards, why not. Crafting material, aetheryte tickets, maybe tomestone gear upgrades in 6.3?

But it's very normal for them to add a mount reward to everything to motivate people to do it. They do it for extreme, savage, blue mage raiding, hunting, fate grinding, leveling all jobs, doing pvp, collecting triple triad cards, doing lots of crafting in the firmament, island sanctuary and I could go on but every major content they add they usually put a mount there to make sure people who would otherwise ignore it try it out.