[muxxa]

Because the bet is that your brain is much superior at figuring out what is important/aberrant and what is normal as compared to the best algorithm you design.

E.g. if you know a co-worker is on holidays then a dearth of checkin sounds will seem normal (ideally this feeling of normalcy will be subconscious). On a different day, a dearth of checkin sounds might alert you that your startup isn't making much coding progress (depending on context not necessarily a bad thing!).