Why no AD supports?

Right now Mages are creeping their way into bot lane, allowing for some neat variation within the lane but I do wanna ask, why are AD supports not a thing. Is it because AD support is simply too feast or famine or is it just not something that's done. Full AP supports with little utility happens, such as Brand, Velkoz, and Zyra. So why not full AD supports with little utility, but more towards AD Casters, so champs focus around using abilities. These champs could include but are not limited to Trundle, Jarvan, and Urgot. All three of those champs have utility that helps their team, but all of them also like at least a little AD to work. So are AD supports not a thing due to being a bad idea or due to them not having a support item that helps. Or can current support items work with AD supports?
Report as:
Offensive Spam Harassment Incorrect Board