What is the reason that you cannot set the tunnel's other side as destination address? Is this because it is virtual only?

192.168.1.0/30 is the subnet I'm using and this is my configuration:

 tunnel1
 ip add 192.168.1.1 255.255.255.252
 tunnel source (doesn't matter)
 tunnel dest 192.168.1.2

**tunnel dest 192.168.1.2** -> Why is this invalid?