What is wrong with this argument?

I don't think it's a good idea to lower the drinking age. Next thing we know kids will get to drive at age ten, and vote at fifteen. Let kids be kids and adults be adults.

Slippery Slope

When a relatively insignificant first event is suggested to lead to a more significant event, which in turn leads to a more significant event, and so on, until some ultimate, significant event is reached, where the connection of each event is not only unwarranted but with each step it becomes more and more improbable. 

Slippery Slope

• If A, then B, then ultimately Z.

• Next thing you know...