Let us contrast two places, Norwich and Bournemouth. Both have been major railway destinations with their own fast express trains, the East Anglian and the Bournemouth Belle among others. They are also about the same distance from London. Population sizes are 132,000 for Norwich and 164,000 for Bournemouth. Travel time is also about the same, around two hours. Yet Norwich is a main line destination and Bournemouth is suburban. Why?
Norwich still retains loco-hauled trains, a decision made by Eastern Region in the 1950s, while Bournemouth went over to EMUs at about the same time. However, the crucial decision was to include Bournemouth in Network South East while leaving London-Norwich as Intercity. However, that may have been promoted by the EMU-based service. It was thus managed by NSE as a part of their grand London commuter network, not as an individual main line. Stopping patterns and ticketing policy reflected this. The Cotswold Line suffered from this as well, despite being loco-hauled in the 1980s. It was far easier. Had it been up to me, both the Wessex and Exeter routes would have been Intercity, but it clearly was not. The alternative would have been to have the whole of East Anglia in NSE, leaving Norwich as a suburban station. This reflects on the city, affecting house prices and encouraging London commuters to move in. As a result, the economic pattern of the local area changes, especially around the city centre. Because commuters tend to prefer out-of-town shopping, fewer people spend money there, thus the local economy deflates. I can't see the City Council liking that.
One might say that this was just main line snobbery, or that it is an inevitable result of sectorisation. Whichever is true, it will inevitably happen again if they introduce EMUs and increase stops on London-Norwich. They might as well extend the Network Card at the same time.