A lot of people have posted calls that actually make very good sense. Consider what would happen if they didn't call. For example, the Up Chatam mainline trains had a small handfull of stops at places like Bellingham and Crofton Park were inserted because the stopping trains on that line were at capacity and people were being left behind at these stations, while some of the passing fast trains had space.
The 2310 from Birmingham New Street does indeed call at Northampton - it's the final service!
The fast trains on between Birmingham and Wolverhampton call at the busiest stations (Coseley, Sandwell & Dudley and Smethwick Galton Bridge) in order to provide more than 2 services per hour on this very busy section of track while maintaining the speed of longer-distance services.
You might say it's a surprise that the 1452 from Aberdeen to London KX calls at Doncaster, Peterborough and Stevenage, but there isn't another train southbound from York for an hour and a quarter after it, so there would be a very long gap indeed for anyone travelling from York or north thereof to Peterborough or Stevnage without this.
These all make very good sense.