The official reason was to simplify the assembly lines by taking out one of the battery configurations. But there was another technical observation to share in the 2018 EVs:
The three 75 kWh Teslas had ranges that were close to the Chevy Bolt but worse energy consumption, kWh/100 mi. Elimination of these three models further separates the Tesla vs everyone else with a wider performance gap.
It doesn't hurt that the 100 kWh pack models have a higher profit and the Model S/X lines are going to two shifts. This also lets Tesla do some assembly line tuning.
Bob Wilson

The three 75 kWh Teslas had ranges that were close to the Chevy Bolt but worse energy consumption, kWh/100 mi. Elimination of these three models further separates the Tesla vs everyone else with a wider performance gap.
It doesn't hurt that the 100 kWh pack models have a higher profit and the Model S/X lines are going to two shifts. This also lets Tesla do some assembly line tuning.
Bob Wilson