Question re BFD configuration for OSPF

 wrote the KB article [1.8.0] Documentation: Basic Bidirectional Forwarding Detection (BFD) configuration for OSPF.

The article is a great help. However, I'd love an explantion for one thing...

The article starts with the basic config for 3 routers. Here's the first.

First configure interfaces and OSPF on each router:
R1
set interfaces loopback lo address 10.0.0.1/32
set interfaces ethernet eth0 address 2.2.0.1/24
set interfaces ethernet eth1 address 1.1.1.1/24
set interfaces ethernet eth2 address 1.1.0.1/24
set protocols ospf area 1 network 10.0.0.1/32
set protocols ospf area 1 network 2.2.0.0/24
set protocols ospf area 1 network 1.1.1.0/24
set protocols ospf area 1 network 1.1.0.0/24

Why is the address set on the loopback?

Could it be set on switch0 instead?

Is there an advantage to setting it on the loopback instead of switch0?

Thanks

Mark