What are the benefits of using the PPP encapsulation type instead of the default HDLC?

HDLC (High-Level Data Link Control) is a bit-oriented synchronous data link layer protocol

cHDLC (Cisco HDLC) was created by cisco to address the HDLC protocol's inability to provide multi-protocol support. Thus, cHDLC frames contain a field for identifying the network protocol being encapsulated.

Ethernet networks are packet based and have no concept of a connection or circuit and also lack basic security features By using PPPoE (encapsulation), users can "dial" from one machine to another over an Ethernet network, establish a point to point connection between them and then securely transport data packets over the connection.

Answer: security