Perhaps this is the rationale. Perhaps not. I think it's interesting that JREast is running some other express services that might be considered non-essential. And I note that there is the Skyliner as an alternative, rapid, and reasonable route to Narita Airport.

In any event JREast is currently forced to weigh its options and make choices about what to run and what to cut - perhaps the decision is based on a combination of factors rather than one simple decision driver.