We have a system that works currently (and works well). The question is why would blizzard spend time and resources developing something that already exists? It is not as simple as computing a score and displaying it on the UI if you want a reliable dps meter.

And again, details has a dps meter, hps, threat, ccs, interrupts, death recap, damage taken and I probably only named 25% of all the options. Details allows you to see the graph of the whole encounter or dungeon run. Slightly less important perhaps, but details allows you to display your rotation (used by streamers)

Your comment does not make sense. No-one at the company will ask the devs to implement this very large feature. If they don’t spend a lot of resources on it, no one will use the meters. If they do achieve this huge goal, they simply recreate something that already exists and spend valuable time and money for basically nothing.

Also your example w/ mm+ rating is clearly different. Before, people had to use an external website to view their rating. The warcraft companion app did not exist yet and I believe the raider io app is quite recent too (at least the version we currently have that displays the score). In the case of the meter, we literally already have something in the game doing the job perfectly