If we aren't allowed to get mounts that belong on the ground then it would restrict the amount of mount designs we can get overall. In history a lot of things that you can ride have been on the ground and suddenly you want us to not be able to get any of these as mounts in the game?
DragonsWhere are the dragons, where are the griffins, where are flying machines?
Alte Roite, Rathalos, Syldra, Midgardsormr, Twintania, Wyvern, Ehll Tou, Diamond Gwiber, Emerald Gwiber, Gwiber of Light, Innocent Gwiber, Ruby Gwiber, Shadow Gwiber, Sanuwa (sort of)
Griffins
Griffin, True Griffin
Flying Machines
Aerodynamics System, Air Force, Al-iklil, Arrhidaeus, Construct 14, Construct VI-S, Construct VII, Cruise Chaser, Dreadnaught, Falcon, Gabriel α, Gabriel Mark III, Gilded Magitek Armor, Ginga, Gloria-class Airship, Gobwalker, Goten, Ironfrog Mover, Landerwaffe, Logistics System, Magitek Armor, Magitek Conveyor, Magitek Death Claw, Magitek Hyperconveyor, Magitek Predator, Magitek Sky Armor, Manacutter, Model O, Prototype Conveyor, Raigo, Regalia Type-G, Rolling Tankard, Safeguard System, Skyslipper (sort of because it hovers above ground), White Devil
All mounts need to be able to fly because when they can't, it's not practical to use them. If there are certain mounts that don't let you fly, why would you ever use them? This was a big problem and all of the ground mounts were not used until it changed.I think the idea to make every mount be able to fly was a mistake, because it seems to have resulted in the devs getting lazy with new mounts where now they don't even attempt to make them make sense flying, they just copy-paste some monster and just give it the ability to fly and don't even attempt to not make it look absolutely ridiculous.
This doesn't mean that all of these ground animals should suddenly be given wings. If we want to RP with them, we can ride them on the ground and when we don't want to RP, we can fly with them and show off the mounts we've earned.