Because it became convenient for almost nothing? Foot passenger only ferries had stopped, all the car ferries were using the eastern docks and even the western docks car ferry terminal/old hoverport is quite a long walk from Marine- though even this is irrelevant as that facility has since become disused entirely.
The liner terminal meanwhile has a single ship every couple of days. That's certainly not enough to sustain a railway station.
As for the western docks, they're a shorter walk from Priory than Marine.
There is simply no good reason to have a railway station at Marine, and there wasn't really a good reason any more when it closed. Note that it closed a few months before Eurostar started operating; blaming Eurostar for its demise is too simplistic as the passenger ferries had already died.
Indeed. My one and only visit to Dover Marine was in early 1993. Passengers for the night ferry to Ostend were transferred by bus to Dover Eastern Docks and it would obviously have been just as easy to transfer passengers from Dover Priory.
Like Folkestone Harbour, they had just become redundant. The historical reason for these facilites to exist had disappeared.
