Accommodation is for adaptations that can't be anticipated or standardized. They are different for each individual. Although we should expect there to be a general willingness to accommodate us wherever we go, we can't expect actual, specific accommodations unless and until we ask for them. We do have to announce, and may have to explain our disabilities a bit in order to get accommodations.
Accessibility is the baseline of equal service, and accommodation is the second step to take when accessibility alone isn't enough.