When I visited Shanghai, I noticed that late at night when there are not many passengers, they will kick everybody off the train at a random stop. They do this with a few trains in a row until there are enough people waiting in the station to fill up a train to some acceptable level.

I assume that the point of consolidating everybody into one train like this is so they can avoid wasting power decelerating/accelerating on a bunch of trains. I.e. just run all the empty ones to the terminus without stopping.

It was a bit annoying whenever it happened to us, but I think this is a better system than getting rid of heavily used local stops entirely.

Edit: As a reply explains, it's possible my description is slightly inaccurate.