The halo vehicles always sell in their limited numbers but there really isn't a huge market for these trucks. Probably the same reason no one has really tried to break into the Jeep market.
What? Huh? If you're putting the Raptor in the "Halo vehicle" space it's not a true limited production vehicle. While it's not sold in F-150 numbers I wouldn't call it a limited production vehicle.
As for why "no one has really tried to break into the Jeep market" it's complicated. The Jeep defines the market it's in. The Jeep IS the market it's in. It's an off road first vehicle that has had its on-road manners improved.
It has solid axles. Short wheel base. Even shorter overhangs. Got lots of ground clearance. And, most importantly, it has multiple decades head-start on the competition.
Making a vehicle better than the Jeep is easy for manufacturers. Making it better off road is VERY difficult with the on road vehicles they have.
Maybe the Bronco will go after it but I doubt it. It likely will be an on roader with decent off road capabilities. But if Ford invests in its off road capabilities in time it could be modified further which could make it more interesting to off roaders.
The vehicle to watch, IMO, is the Baby Raptor! If done right it will beat the Chevy Colorado/GMC Canyon and the Taco. And it could even take sales away from the upcoming Jeep pickup assuming it has good (low speed) off road capabilities.