I guess because ive been flying for so long, I just assume all pilots would know the history behind the need for SOMETHING to be said (and why) upon the radio altimeter coming alive.This is variously responded to with a call such as "terrain" "radio altimeter alive" or "twenty five hundred" or even "check" but not "checked".The reason for this is as always, situational awareness.Are you expecting terrain as this point? If not then this may be an early warning of something bad about to happen.It seems that this type of call became common place after the Air New Zealand DC10 accident, where no action was taken by the crew upon noticing the RA coming alive.Also the accident itself if I recall correctly was the reason why the GPWS response became what it is today.It is possible, just, that if that crew used todays GPWS response the accident may have been averted thus saving nearly 300 lives.
Many times in the SIM when I notice crews ignoring the RA alive call I later give them a hard GPWS out of nowhere and many many times they have crashed.Lesson learnt hopefully.