For me it's just the opposite - a "customer" is someone who buys something in a shop, it's basically a financial transaction, whereas the term "passenger" conjures up the image of a (pampered?) guest, well looked after on a train.
Additionally, the term customer for me, in the context of railways, just reeks of enforced ideological free market dogmatism, imposing a bleak, 'balance sheet' above all else, soulless transactionism, on what was previously a wholly different relationship.
Should English students, now they have to pay thousands for their education, be retermed "customers" as opposed to "students"?