Do you actually have systems that implement the UDP echo service? Since it enables "ping-pong" and "Fraggle" style attacks, systems have generally shipped with it disabled by default (or not even implemented) since the late '90s.

There is no place to provide SNMP credentials with which to do a pingSnmpQuery, although I suppose you could have some defaults.

Similarly, there's no place to provide a TCP port number for a pingTcpConnectionAttempt.

I think the other values were fundamentally things that the remops working group thought might be nice but didn't really think through completely, and there hasn't been a great demand for implementing them.