It's actually very difficult to either cut services or make them slower due to govement red tape, you can of course add more very easily.
In Bicester where I use to live the main A41 London road has a crossing with a station next to it like OB, the track use to be single line to Oxford with the station the correct side of the road hence minimal disruption. 3 years ago the Train operator applied to change the line to duel and link it with the Birmingham to London line. This requires crossing the road and with 3 trains an hour in each direction together with the requirement to close the crossing while the train is in the platform results in the crossing being closed more than its open, it has caused chaos but nothing will change due to the above.
The rail system needs a major overhaul but if you look at the state of HS2 it won't be in my lifetime.