Dialplan error: "No application for 'Originate'"

I’m trying to do originates from within the dialplan (driven by * 1.8 ) by calling a context with code like the following:

  exten => s, n, Set(i=0)
  exten => s, n, While($[${i} < ${targetcount}])
  exten => s, n, Set(i=$[${i}+1])
  exten => s, n, Set(target=${CUT(targets,",",${i})})   ; targets is a string with a list of #s like "103,104,105,110"
  exten => s, n, Originate(SIP/${target}@someHost,app,Playback,sound_file)
  exten => s, n, EndWhile
  exten => s, n, Hangup()

When I call this context I see the following error outputted to the CLI:

pbx.c:4218 pbx_extension_helper: No application 'Originate' for extension (broadcast, s, 9)

As a side note, using “Action: Originate” from AMI works just fine, implying that the Originate command is in fact installed. Why can I use Originate from AMI but not in the dialplan?

EDIT: Doing a “core show applications” reveals I do not have an Originate application installed. Manually loading the app_originate module fixed my problem. So my question is why does AMI automatically support Originate but Asterisk does not?