Because they have told us over and over and over and over that they want us to. That’s how they improve how sharding works.
Nope. More like:
Time: 14:23 Illidan Server Time
Location: Stranglthorn Vale
Description: A raid of about 20 Alliance went around ganking people leveling in the zone. A Horde raid was organized to combat them, reaching about 25 people. When we engaged the Alliance, one of the raids was sharded away.
That way they can go and look at what happened in Strangthorn Vale at 2:23pm Illidan’s server time. They can see what the servers were doing and how/why the sharding mechanism kicked in.
With that data they can help develop additional parameters that govern sharding because right now, from the sound of things, it is looking at pure numbers and grouping.
Whining does not help improve the system. Nor no demands they turn it off forever (Spoiler Alert: They won’t). But giving them reports like that help them fix the problems you’re having.