Because the FF5 version isn't really a buffer like the FFXIV one is.

The FF5 version has Air Steps, Find Pits, and Gaia. Air Steps equals suspend. Find Pits doesn't exist so you just have to test and see what aoes can be suspended over.

And then we have Gaia, it did debuffs and/or damage attacks randomly based on what terrain you are on. The FFXIV version is weather based and instead works as group buffs and a heal. So if we were to have it more like its FF5 version, it would be basically gambling during a critical encounter for better and for worse. So for example, lets take an easy boss like the Trade Tortoise. Its terrain would be Beaches. Therefore the random attacks the Geomancer could've done would be:
  • Tsunami (low water damage)
  • Big Tsunami (medium to high water damage)
  • Waterfall (high water damage)
  • Whirlpool (reduces enemies health to a single digit)
  • Phantom (Kills one enemy. Does not bypass target's immunity to Death but Kills Heavy enemies. Fully heals the undead.)