Managing loco changes requires a fair amount of infrastructure.
1| Crew lobby - If the station is handling a lot of loco changes, then adequate facilities will be required for the crew (LPs, ALPs etc).
2| Parking lines for locomotives - Dock sidings or parking lines will be required for the locos
3| Trip shed - Depending on the number of LCs being...
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done, a trip shed with all the necessary staff and facilities for maintenance are also required.

Now the electrification is progressing on these routes and will be completed in an year or two at the most. For such a short period, there is no point in setting up all these facilities at intermediate stations (they will be unnecessary after complete electrification), so LCs will mostly be handled at already established points.

Setting up all the facilities for LC at intermediate stations just for a few months is an unnecessary expenditure.