Card access, although it can be initially more costly than it's keypad counterparts, allows for much greater flexibility within a facility. It will allow specific individuals access at specific entry points during specific hours.
Proximity cards are nearly indestructible, easy to manage, and if an employee misplaces one or has one stolen, it is a fairly simple and inexpensive procedure to remove the missing card from the system and issue a new one to the employee, WITHOUT changing anything for their fellow employees. This was definitely NOT an option with physical keys.
Most of these types of systems have audit trail capabilities. This creates the potential for generating time and attendance reports directly from your access control software.
Some even allow management over existing network infrastructure, providing you with the ultimate in flexibility while cutting installation costs substantially.