(08 Mar 2015, 12:31 am)tyresmoke wrote They have, that's the job of the X21. They'll never go South from Durham as the X12 is heavily used by Durham University students (& staff) hence why it runs until 3am on Fri/Sat nightsWell I'd never say never... When Arriva (and Stagecoach NW) neglected their customers on the Tyne Valley, they were sharp to introduce a new express service which soon became rather popular indeed, stealing a lot of customers from the long established 685 service in the process.
Similarly, following the withdrawal of Arriva's 31 (etc), there was a gap in the market for journeys from Sunderland to Middlesbrough. As they had connections at all ends (albeit very few at the southern section), it's worked very well and proven to be a commercial success.
Resources are easily allocated elsewhere to allow for new commercial ventures to take place. It's the market research prior which determines whether it actually happens or not...