This is because major studies have shown they have no major positive effect over regular soap.
They actually help spread disease.
However, they do not do it directly. They increase the resistance of Bactria to the common antibiotics, which is extremely dangerous for us. Developing new ones is extremely hard. In fact the last new class of antibiotics was found in the 1980s.
Researches infected people with a weak bacteria that could only effect people with weak immune systems and had them wash their hands. No measurable difference was found. Although if you put it in test tubes with the bacteria and wait a minimum of 9 hours....
The most common antibacterial in them is triclosan and it is horrible for the environment.
It effects hormone regulation in animals, Kills algae and even makes them resistant to the antibacterial.
Gaining resistance is bad news, it means that antibiotic won't work on that strain which means others must be used. When a bacteria becomes resistant to all of them we have it becomes a super-bug. The only thing we have for that is quarantine. This is amplified when it literally builds up in ours lakes and rivers.
Sadly the ban only to 19 active ingredients.
Information sources:
http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm517478.htm
http://www.sciencealert.com/fda-bans-antibacterial-soaps-because-they-re-not-better-cleaner-or-safer-than-regular-soap
image source: upload.wikimedia.org/wikipedia/commons/thumb/4/4d/E-II-R-soap.jpg/1024px-E-II-R-soap.jpg