Is this alongside the carpark? It may be that the wall of railway sleepers isn't considered high enough, but the only time it might be a revenue problem is if there is a blockade at the normal exits.
OTOH▸ maybe it helps prevent damage to parked cars - who knows where the local kids have been landing when they've vaulted over the 'fence'...
PS Perhaps we are too suspicious and it may just be normal station improvement works - a number of stations in the area (such as Swanwick) have had new lighting, fencing, surfaces etc; and it hasn't really been revenue related at all...
Paul