This may be worth sticking in Management and Infrastructure, so if you want to move it, feel free.

I have often thought about this and haven't had a good way of explaining it, so hopefully it will make sense.

GNE often pump prime certain route corridors with one or two services. As well as this, they introduce less frequent services, which in several instances are then withdrawn after a short period of time, due to a lack of customers.
Using basic maths and one or two corridors, I am unsure as to why the less frequent routes would ever attract passengers.

THE ROUTE FROM PARK LANE TO FULWELL MILL I.E NEWCASTLE ROAD
On this stretch of road, you have the X3, 9 and 35/35a. Using basic ratio, the services are: 2 : 2 : 6 ph. Excluding passengers traveling beyond Park Lane or Fulwell Mill, the probability of getting anything other than the 35/35a is very low. Even with the X3 and 9 evenly spread out over that 15 min period upto 2 35s can take these passengers. When you factor in the metro to Seaburn the ratio is then 2 : 2 : 6 : 5 ph.
Yet GNE seem surprised when passenger numbers are low on the X3.

THE ROUTE FROM PARK LANE TO GRANGETOWN/RYHOPE
On this stretch of road, there are the 38, 39, 42, 60, 61, 238 and X7. Again, using basic ratio, the services are: 2 : 3 : 6 : 6 : 6 : 1 : 1 ph.
These services have just been changed/adapted, but it doesn't take a genius to work out which will be the most popular, which ones will vanish without a whimper, or if you turn up at a bus stop which services will turn up 1st and I haven't even looked at the Stagecoach or Arriva services which can get you to Grangetown or Ryhope.

If apply this same method to other areas, looking at services which were quietly stopped, it is pretty obvious why they were stopped and why certain routes don't make money.
Durham Road in Sunderland with the 20s, 35s and X35 opposed to the 71?

There will be plenty of other examples too between towns, villages and/or cities.

One other point to make about in frequent services compared to infrequent ones.
Imagine you are in Seaham with a red zone ticket and have just missed the 238 to Houghton, so you have a choice of waiting another 60 minutes for the next one or jumping on a super frequent bus to Sunderland and change, knowing you will be home before the next 238 gets anywhere near Seaham...

Having such a mixed network of frequent and infrequent services is going to cause these continual changes and unless something major happens, we as passengers will continue to see change after change after change on the services.