Why is diagnostics_agent "inherently inefficient" and what to do about it?

Question

I have a clean install of 10.11. When I boot the system in my own admin account, with no login services enabled, nor any internet or cloud accounts enabled (e.g., Messages, Facetime, Mail, Calendar, etc.), I see on Console the following message:

10/4/15 2:12:08.104 PM com.apple.xpc.launchd[1]:(com.apple.diagnostics_agent) This service is defined to be constantly running and is inherently inefficient.

Hopefully, my question should be a simple one for folks who have more experience with the OS than me: Why does this service exist if Apple's own OS admits that it is "inherently inefficient?" If it is "inherently inefficient," then how can users disable it without having other services flip out or register warnings/errors on Console?

N.B., there are other services that have the same message in Console, like AirPlayUIAgent:

10/4/15 2:12:08.097 PM com.apple.xpc.launchd[1]:(com.apple.AirPlayUIAgent) This service is defined to be constantly running and is inherently inefficient.

I can't be certain, but I think this also occurred on Yosemite--i.e., I don't think it's an El Capitan specific question. Help understanding these messages, functionality, and behavior is appreciated. Help disabling or altering them is also appreciated.

Solution

Here is the answer (found here):

The inefficiency refers to energy usage. Since it never shuts down and runs constantly, there is no efficiency by definition (theirs).

The Diagnostics_Agent is by definition always running, thus triggering the above message. It's not an error, it's a feature!

I found this when trying to eliminate the huge list of reported data in my Console, and discovered it's just the diagnostic daemon doing its thing. It is not necessarily sending it anywhere.