Roughly 315,000 people in the entire, mostly rural county versus 289,000 in the large city of Newcastle dictates where and how the money is spent.
Berwick, Alnmouth and Morpeth have the type of intercity services most counties can only dream about. The county as a whole is far from hard done by.
More could be done for a few areas such as Cramlington and the surrounding area however the cost of it could could make it poor value.
Whilst Berwick, Alnwick and Morpeth are all relatively small towns in their own right, they are effectively the railheads for most of north-east Northumberland. Morpeth is the railhead for Blyth, Ashington and Bedlington, Berwick covers a big chunk of the Borders as well as far north Northumberland and Alnmouth covers the middle of the county.
Travel to Edinburgh or Newcastle isn't too bad, with an hourly service during the day. Inter-county travel on the trains is extremely difficult though. There are very few trains which stop at all three stations in Northumberland, and these tend to be at the start or the end of the day. Links between Berwick, Alnwick and Morpeth are very poor. There isn't a train that calls at both Berwick and Alnmouth between 1149 and 1749; there isn't a train that calls at both Berwick and Morpeth between 1048 and 1917.
The weekday service at Cramlington isn't an issue, it's hourly all day both north and south, and I don't see that that needs improvement.
The idea of installing a Morpeth by-pass is a very poor use of money though. The slowing down for the curve doesn't cost that much time. I'd rather see the Blyth & Tyne re-open, with an hourly train each way round the loop, long before we spend the huge sums needed to ease the curve at Morpeth.
I still think the best use of the capacity is 1tph XC and 1tph VTEC non-stop Edinburgh-Newcastle, 1tph Scotrail/Northern semi-fast (Dunbar, Berwick, Alnmouth, Morpeth, Cramlington) with occasional stops at the small stations north of Morpeth.
To get slightly back on topic, I'm not sure of the point of Scotrail running as far as Berwick upon Tweed. It seems a waste of paths. If they're not going to run semi-fast all the way to Newcastle I don't see the point of extending the Scotrail trains beyond Dunbar.