This is because some legacy computer systems, especially the "central reservations systems", have failed to comply with the standard, notwithstanding the fact that it has been in place for 20 years.
Hal ini karena beberapa sistem komputer warisan, terutama "sistem pemesanan pusat", telah gagal memenuhi standar, terlepas dari kenyataan bahwa ia telah diterapkan selama 20 tahun.