some train companies aren't good at actually providing assistance, even when booked. often the train arrives at the required station, and the assistance isn't there, leaving the person stuck on the train. the train conductor then has to walk to get the on-train ramp (invariably it's at the other end of the train), deploy it, get the person off and then re-stow the ramp.
all this takes time and often the train collects a reportable delay, which has to be attributed. often this goes down as "passengers causing a disturbance", which kinda shows the attitude of some train companies to their less able customers.