Аутентификация DUN

MS-CHAP is an entirely different type of protocol than LM/NTLM/Kerberos, and is designed to secure an entirely different set of things in a completely different environment. MS-CHAP is a WAN protocol, whereas NTLM/Kerberos are LAN protocols. MS-CHAP provides no authorization features, whereas Kerberos provides very sophisticated capabilities. I should also point out that the MS in MS-CHAP means Microsoft, so MS-CHAP is definitely "natively supported".

MS-CHAP and PAP are authentication mechanisms designed to work with tunneling line protocols like SLIP, PPTP, PPPOE, etc. Line protocols are primarily concerned with multiplexing a virtual circuit between two endpoints over an [analog] carrier, like a telephone line. They are very low level protocols, which must operate with minimal bandwidth and computational overhead. MS-CHAP is applied to the line protocol as a mechanism for RADIUS authentication. Line protocols are generally considered WAN protocols, and are expected to traverse unfriendly networks between endpoints.

Line authentication protocols like MS-CHAP and PAP are designed to authenticate a terminal that has at most a transitory relationship with the network its authenticating on. These systems may connect to many different networks, and should involve no setup beyond configuring the connections arguments.

LM/NTLM/Kerberos are service-level authentication and authorization protocols, paired with service protocols like NETBIOS/SMB/LDAP. These sophisticated protocols are designed for situations where the computer is more or less permanently connected to the network it is associated with, and require a lot of infrastructure, so the setup of the machines is rather invasive (like joining an MS domain, configuring WINS servers [for LM/NTLM], etc). Kerberos in particular requires bandwidth for frequent re-authorization traffic, and while still computationally trivial, it is a far weightier scheme than the line authentication protocols. All these service protocols are LAN protocols, and are not generally exposed to the WAN, where there would likely be security, performance, and reliability ramifications.

Perhaps the question you should be asking, is why PPP/PPPOE/PPTP have not been replaced by protocols like IPSec or L2TP, which are modern WAN-Safe tunneling encryption protocols commonly used in VPNs (the modern remote access method of choice). Here is a list of common authentication backends for the Cisco VPN client: http://www.cisco.com/c/en/us/tech/security-vpn/authentication-protocols/index.html

The reason MS-CHAP is still around of course, is legacy compatibility. Modernizing a large enterprise's remote access system is a costly endeavor, I suppose.