Daily active users is a number that survives every reorganisation because it is short and it sounds like vitality. An app can raise DAU by moving a token refresh, by putting a weather glance on the lock screen, or by letting a household share a login. None of those are product-market fit. They are plumbing, chrome, and manners.
We ask rooms to pair DAU with a completed job: a track finished, an order submitted, a document exported. If the job line and the DAU line divorce, believe the job. The audio case in our alumni letters is the textbook: Bluetooth taps had been counted as love. Unbundling them made D7 look unkind and commissioning look sane.
Shared devices are the second liar. Education apps, kitchen tablets, and shop-floor scanners will inflate a “user” until identity stitching is treated as a first-class module rather than a weekend for the intern. Identity week on Signal Architecture is unpopular for this reason. It is also the week that stops a school from reporting 4,000 daily children when it has 900 devices.
Push opens are the third. An open is not a session if nothing is completed. You may still send the push. You may not file the open under engagement in a board pack. The Retention Atlas forbids that claim in writing because slides forget spoken caveats.
None of this means DAU is useless. It is a decent smoke alarm. Smoke alarms are not strategy. If your only daily chart is DAU, you are measuring whether the app was touched, not whether it was needed.