I suspect the track and derailers were left as it was easier to remove the odd rails and leave everything else until some other job actually required some serious effort. I think the derailers are/were incorporated into the interlocking so removal might have been a substantial bit of work.
John; sorry for the delay but your suggested explanation seems to tie in with the apparent evidence. Going into work this morning, I kept an eye out for the derailers and noticed that they seemed to be connected to some sort of control gear - your suggestion re: the interlocking seems very logical indeed.
Exile - just out of interest, what times were you travelling? My work patterns mean that while I usually travel in the standard peaks, I do get to experience mid-morning and early afternoon "traffic" too. My observations are that the peaks are generally packed - then there seems to be an artificial peak of about an hour just after the real morning peak, after which it calms down for an hour or two (40ish per train sound about right?) and then steadily builds to the afternoon rush. I've also found that the semifasts and expresses are often considerably busier than the stoppers once outside Liverpool itself, though I guess that this is to be expected.
I must admit, this week is a welcome change - this is the first week that it's just been crowded, rather than crush-crowded as it's been the past few weeks what with school holidays and Big Liverpool Events.
This said, the 1831 Wigan NW service tonight had it's recent usual formation halved from its (welcomed!) double donkey down to a single. Crowded until about Huyton when seats started to become available. I think after Prescot, anyone who wanted a seat had one.
In fact, as a rule on that line - I tend to find Huyton or Prescot tends to be where the remaining passengers can breathe out a bit
Ha - Rob, just read your post as I was about to post mine. It wasn't the 1831, was it?
-David