There is definitely a benifit, it just doesn't necessarily have to be for the bottom line. If you are running a major publisher you are likely spending public shareholders money or executive partners money (with some skin in the game yourself) on these games.

At the very least based on the consistency some publishers use Drm we know getting Drm buys piece of mind/job security that whoever is managing the project is doing something to prevent shrink/theft.

It's like the ad line goes, nobody ever gets fired for buying an IBM.

There is safety in doing the best practice or industry standard.

That all said, it's entirely possible there is hard data out there that strongly suggests there is a cost benifit too it, and it's just not public data.