Well I had a big long post about this Saturday morning before we experienced some forum issues. All seems well now so let me try one more time.
JP is right again. I went through the Epona fluff and the first since says "the only Clan to manufacture and deploy the Epona. Other Clans consider the pod technology wasted on conventional vehicles..". So there is no direct contradiction as I originally thought.
Apparently the Bandit and the Badger were early Omnitech attempts that were abandoned by the Clans. Ice Hellion mentioned the Elemental and I think that is an another important reason why these Vehicles disappeared.
My contention in the rapid tech development that was the Golden Century the OmniVehicle was a natural follow up to the OmniMech which was first fielded in 2854. The Badger and the Bandit (likely the first and most successful) were quickly developed as OmniVehicles since they did not suffer from complex problems like gyroscope issues involved with BattleMechs or higher tech Aerospace Fighters.
I will let Blood Spirit Vehicle Orthodoxy (Field Manual Crusader Clans pg 25-26) speak for itself next.
According to the doctrine of military deployment as set forth by Nicholas Kerensky, one Cluster equals five Trinaries-three 'Mech, one vehicle and one infantry. Aerospace forces were not integrated directly into the units, but were kept separate, to be attached to other forces when needed. Clan Blood Spirit has taken this organizational structure not as a mere suggestion, but as a mandate for all time.
Following the death of Nicholas, and moving into the Golden Century, fascination with the BattleMech led to a decline in vehicle use among most other Clans. When Clan Coyote introduced the OmniMech, this fascination became an obsession for most Clan warriors. Though MechWarriors have generally felt their machines superior to armored units since the invention of BattleMechs in 2439, the Clan caste system, combined with the new OmniMech, led to a sharp devaluation of vehicles in almost every Clan. Relegated to defensive roles, the vehicle was seen as "the poor man's machine." Honor, for a vehicle crew, did not exist. In the first few decades following the invention of the OmniMech, most Clans began to remove their vehicles from frontline and even many second-line units, replacing them with aerospace fighters. Though each Clan still fielded small amounts of armor, the Clans as a whole began refusing to admit that such forces even existed
While this fluff indicates the OmniMech as the main culprit lets not forget the innovation of the Clan Elemental by the Wolves in 2868. OmniVehicles would offer a certain tactical advantage but that would be negated by their fragility and high cost especially when compared to the more durable Mech/Fighter along with the sudden protection and mobility given to infantry thanks to practical Battlearmor. Despite some institutional resistance to organizational reforms (I do believe more traditional Clans would be slow to change Kerensky's Unit Structure) the effective performance of new units would force most to change until only the Spirits and the Horses are left. There is also the limited warfare angle to cover which would frown on OmniVehicles. It favors individual honor (not for vehicle crews) over the total war attitude of just win damn it. As a result when ilKhan Victoria Ward enacts the Uniform Designation Protocols in 2883 (specific date from the Chaeronea fluff) the Badger and Bandit are likely on their way out.
Only to be dusted off by the Wolf Dragoons. I still wonder if Kerlin Ward did not include them to give the InnerSphere a chance to glean Omnitech.