I worked on some of these systems as well. Credit card details haven't been sent by emails for many many years, and I believe the last fax Booking ever sent was somewhere in 2018 or 2019, the whole fax system was decommissioned. By the time I left I believe they were still showing CC details to hotels via the extranet or an app though. A virtual CC thingy exists, but like someone said upthread, hotels are very set in their ways and often behind the times.