These systems also regularly fail for travellers who don't fit the assumptions developers make about users. For instance the app might not be available on the a

These systems also regularly fail for travellers who don't fit the assumptions developers make about users. For instance the app might not be available on the app store for foreign users, or might require a local phone number, or might enforce a format that does not match the user's data. They frequently fail for groups who complete a task together, or people who act on behalf of someone else.