Because they want you to buy a new one. Seriously. That's the same reason they engineer a lifespan into everything you buy. They ran out of the ones they had and decided not to provide that option Any longer. As they are no longer selling that model truck. If you want a ranger with a brake controller you'll have to go aftermarket or if ford had their way, a new ranger.
I assume it's been discontinued since the 5G is no longer produced and the 6G Ranger doesn't use it. The non-Ford branded redarc works great it just won't activate the trailer brakes during a AEB event.
Ford has been on my shit-list for a while now with their options. I can't built the F150 I want with tow mirrors, can't get a 2.7 Ranger without 4WD, can't get the brake controller in an XL Ranger.
F-em.
What were we talking about? Ohh, brake controllers... Yea, they just didn't buy more from Redarc when they ran out.