Why are Point-to-Point WAN protocols simpler than other protocols?

Only two nodes share the link, so frames can only go to or from those two — no complex addressing or media access control is needed.

Point-to-Point topology characteristics:

• Directly connects two nodes only
• The nodes may not share the media with other hosts
• Because all frames can only travel to or from the two nodes, protocols can be very simple

Key insight: There's no need for complex addressing or media access control when only two devices share the link.

Go deeper:

• Point-to-Point Protocol (Wikipedia) — defines PPP as a link between exactly two routers with nothing in between, so no shared-media addressing or contention is needed.
• Point-to-point topology in WAN context (Study-CCNA) — shows the point-to-point link behaving like a direct dedicated circuit between two sites.