At smaller stations and those where track crossings have been removed station staff may not have the necessary permissions to go down onto the track, so yes, in that situation if the object in question is a distance away from the platform edge it might not be retrievable immediately.
Couple of personal experiences. I've occasionally had to tell people off for sitting with their knees over the platform edge. They always give me the "surly teenager" look (regardless of their actual age) because I'm obviously being a jobsworth and what would I know?
A former colleague of mine was a on a train that struck someone doing that. The person survived but they won't be getting on a train unassisted again.
Whilst I try and keep an eye on what trains are doing, I'm not omnipotent. I once had a diverted high-speed service go through the station; the first warning I had was when it was passing. It would have been nice to have been informed beforehand, but in that instance for whatever reason I wasn't.
Even if everything is set up correctly, you can still have incidents like those track workers who were killed by a runaway work trolley because it turned out the contractor had sloppy maintenance practices.
Edit: I used the phrase "tell people off", which does give an impression of being a jobsworth. It would be more accurate to say that I request that people place their legs back in a position of safety.
