ASUS delivers the same model with different specifications, and it means the model in your case K53E series can have USB 3.0 but not all the submodels like yours K53E-B1.
I own an ASUS laptop and I know that the drivers that you find on their support site for your particular model also includes for other submodels that might have USB 3.0. For the model I own they have also added a USB 3.0 driver but my laptop doesn't have a USB 3.
The USB 2 works fine for me and I can't complain about the transfer speed at all.
You can read about your models different specifications here: ASUSTeK Computer Inc. - Notebooks- ASUS K53E