At the time the specs were released for the 2012 Rebel, no ABS was in the specs.
Adding ABS would be a major challenge. The rear brake is a mechanically actuated expanding type (drum brake).
From the factory it could add about $1000 to the price tag. I have no idea what it would cost to design, engineer and install it on a one off basis
1987 CMX250C Rebel
2002 FSC600 SilverWing
1983 Yamaha Midnight Virago XV920MK
Put your bike's year and size in your signature.
It helps others help you.
A majority of the big inch cruisers come with ABS.
As mentioned, it adds to the pricetag. Smaller bikes become tougher sells in a "bigger-is-better" marketing mindset when you raise the prices up to big bike levels.
Although if you really set your mind to it, I'm sure the CBR250 front caliper and ABS control unit can be adapted. But once again, at least considering how new the model is, you'd be paying through the nose to acquire the components (the option on the CBR is a grand itself to the base price, and no doubt costs even more when ordred separately).
"Ride Safe, Chop Safer" Motorcycles are not unsafe. However, they are extremely unforgiving of inattention, incompetence, ignorance, and stupidity.
Dismantling, sawzalling, and rattle canning does not make a bobber. That's called an "ANCHOR". http://shadow-shack.20m.com