End credits on a large film can run for ten minutes. The length is not ceremony, it is the sum of obligations that each require a specific name to appear.
A credit is an entitlement
Credit is negotiated in contracts, specifying the wording of a title, its position in the sequence and sometimes its size relative to others.
Union and guild agreements set further requirements, defining which roles must be credited and in what form.
Once established as a right rather than a courtesy, the list can only grow, because removing anyone requires their agreement.
Disputes over the order and wording of credits are settled through formal arbitration in some categories, which indicates how much value the parties place on them.
Visual effects multiplied the names
A film with substantial effects distributes the work across multiple companies, each employing large teams on specific sequences.
Every artist who worked on those sequences has a reasonable expectation of being named, and the totals reach into the thousands.
The work is also fragmented, with individual specialists on lighting, simulation, compositing and tracking, so one shot can involve dozens of credited people.
Vendors change during production as shots are reassigned, and each company that touched the film expects its team listed, so the totals accumulate rather than replace one another.
Production support grew as well
Modern productions employ larger crews across catering, transport, safety, and coordination, and each of those departments is credited.
Filming in multiple countries duplicates whole departments, since a second unit in another territory has its own complete crew.
Companies providing equipment, insurance and financing also appear, which adds corporate credits alongside individual ones.
Music and legal obligations add more
Every licensed piece of music requires its writers, publishers and performers to be listed under the terms of the licence.
Filming locations frequently require acknowledgement as a condition of access, as do organisations that provided advice or equipment.
Legal notices, copyright statements and jurisdictional declarations occupy their own cards at the end, none of which anyone reads.
The post-credit scene made it a problem
Placing material after the credits converted an optional sequence into one a portion of the audience feels obliged to sit through.
Cinemas dislike this, since it delays cleaning and the next screening, and it compresses the turnaround between showings.
Some productions now place principal credits earlier or run material during them, which is an attempt to solve a problem the same industry created.