So do the validators that are put in waiting areas, inside the trains, etc. in cities with no gates. That you can literally use at the time you want to use them (waiting for the train, inside the train, etc. ) , rather than forcing a bottleneck to everyone.
> As others have already said, Japanese gates are open by default
And this by itself already makes more of a latency difference than the entire IC card system does. Imagine what removing the gates altogether does.