The implies gate, signed as A->B, performs a useful function. When A is off, the output is on no matter what. When A is on, the output is B. This may not seem useful, but it is useful for current inhibitors (when the output is inverted) and things where a signal may need to be forced (door locks, etc).
In classic gate terminology it is an OR gate with input A inverted, which will only turn off when A is on and B is off.