And, DIR is much more than equipment. Another part of it is training and standardized reactions to emergency situations. As an example, a DIR diver will be able to respond quickily and in a standardized fashion to an OOA and solve the immediate problem of getting breathable gas to the diver in seconds, consistantly, every single time. There's also a strong focus on teamwork and awareness. Once the basics are down a lot of DIR training becomes throwing more task work on the team (lines, bottles, lost masks, etc) and figuring out how the teamwork breaks and team-members become task focused, etc and then training again to fix those problems. This may sound a little like overkill for recreational diving, but things like situational awareness and prioritizing problems are things that are mentioned in Rescue courses, but there's no systematic approach to really finding the issues and fixing them.
As lamont so often does, he has nailed it.
The system makes sense. The education is superb. And putting everybody on the same page makes for some very enjoyable, relaxed, confident diving. It's not the only way to dive, but I've found it a very good way to dive, and the people who have adopted at least the core of the system to be very good people with whom to dive, and absolutely superb people with whom to have a problem underwater.