How does interface status and line protocol work in switch and router ?why the behavior of the interface status is different in switch and router , as switch depend on peer interface status for its own status and router dont ?

Interface Status and Line Protocol : 

Router  :  In case of Router by default all ports are administratively shutdown as per it;s status show .

Switch : in case of switch by default all ports status is down ( admin it's up ) until and unless some other device is connected at other side of a switch. because when some other device will be connected to a port of switch it will send KEEP ALIVE and link will automatically come up.

Router : Router show the same behavior when port is administrative no shutdown and recived keep alive ..as line protocol state up.