Access Control is an important part of security.
It restricts access to just approved personnel, protecting your site.
It requires the proper hardware & software installed to perform properly and to have the desired features needed.
After that is accomplished, it needs to be determined how the visitor or employee, will be granted access.
This can be accomplished by a card, tag, cell phone, keypad, fingerprint reader or facial recognition.
It really boils down to how secure is your need and your budget.