You're very quick to judge on scant information! The track and signalling design specifically include for later installation of a third through platform arrangement without having to change the new junction, but planned operations don't require it yet (all planned passenger workings call at Rochdale anyway).
It isn't as simple or cheap as you claim - a new junction is required at the Rochdale East end, a new underpass bridge (If you'd actually visited Rochdale you'll see there is a hole), reconstruction of the platform front wall to modern clearance standards, complete resurfacing and fencing, a lift, lighting, PA, CIS, CCTV, a waiting shelter and signalling changes back to Smithy Bridge LC.
Since I'm guessing you're a good citizen and pay your taxes, would you prefer NR to gold-plate everything? All I hear from your kind is that NR spend too much money as it is, so please choose a viewpoint and be consistent.