If the destination is unreachable, then the router will drop the packets, but will also generate an ICMP destination unreachable message to the sender.
This would be good in an internal network because it will speed up failure detection.
Also, when not using an OS that wants to hide all technical messages from the user, it gives you appropriate diagnositic messages.
PING 192.168.10.1 (192.168.10.1) 56(84) bytes of data.
From 192.168.1.1 icmp_seq=1 Destination Host Unreachable
From 192.168.1.1 icmp_seq=2 Destination Host Unreachable
This tells me that the 192.168.10.1 host is in an unreachable network, and that the 192.168.1.1 router is telling me that.
When there are other hops towards the destination that do not have the unreachable route entry, it tells me where that entry is located.
Often quite useful when looking for errors in a complicated network with autorouting (BGP, OSPF) etc....
But you know all about that