If there was untapped potential for demand you would have pictured one of the local bus companies tapping into that demand by running a bus between the two places.
Like the number 2? Takes 30 mins to do a journey that a train (when it runs) covers in 10. Runs hourly. Doesn't provide as convenient connections to Warrington and Manchester as a train would, and there are plenty of people who wouldn't consider catching a bus even if it did run at a reasonable speed.
Come to think of it, if you wanted to get from Ellesmere Port to Runcorn you can do so by train in a mere 29 minutes (vs 1hr 42mins by bus or 1hr 12mins by train via Lime St). Great. Just so long as you don't mind getting up for an 06:30 departure and Northern actually bother to run their train. Pointing at this line and saying "no one uses it" is just as ridiculous as it was in the 1960s when services were deliberately run down to justify closure. Of course no one uses it, it's almost unusable. Who would use a service that only runs at times that mean a 12.5hr day (again, if it even turns up)?
Incidentally, for some reason the Passenger Flow Data lists Runcorn East as having 3,450 passengers heading to/from Eastham Rake. If they are all travellling on a permitted route (and not buying the much more expensive "via Liverpool" ticket) that would make a total of up to 14 people travelling in each direction per day - via Chester apparently isn't permitted and via Liverpool is more than twice the fare. You can't travel in both directions on the same day, even if Northern did run the advertised service, because you'd have to turn back before you got there or you'd miss your return. So presumably you have two sets of 14 people travelling in each direction per day, staying overnight in Eastham Rake. Maybe they all hold a Changing of the Guard ceremony on the Ellesmere Port footbridge.