Let us face it, OEM (Original Equipment Manufacturer) parts are expensive. That includes taillights.
Especially for trucks, most stock taillights are not bright enough because their housing isn’t large enough like those in sedans or SUV’s.
The design of a truck dictates that its taillight be confined to the corner-most section of the vehicle. The farther apart the lights are, the more a manufacturer can claim that the truck has a large bed- which is a selling point for trucks.
All that without accounting for the safety that comes with visibility. And OEM lights cost a fortune!