Notifications are effective because they exploit a response that operates before any decision is made. Their design follows directly from what reliably triggers it.
Orienting happens before choosing
Sudden movement, novel sound and changes at the edge of vision produce an automatic turn of attention that precedes deliberation.
This response is not optional in any useful sense, and treating resistance to notifications as a matter of willpower misidentifies what is happening.
Design choices follow: alerts appear with motion, arrive with sound and use colours that stand out against an interface deliberately kept plain.
Unpredictable timing sustains checking
Alerts arrive at intervals the recipient cannot anticipate, which is the pattern that most reliably sustains repeated checking of a device.
Predictable delivery would allow a person to check once at a known time and ignore the device otherwise, which is exactly what batched delivery achieves.
Services that offer batching typically make it a non-default setting, since the default determines what nearly everyone actually experiences.
Counts and badges work without any content
A number on an icon indicates that something is unresolved while withholding what it is, and the incompleteness is what draws the check.
Because the badge carries no information, it can be shown for anything at all, including items the recipient would ignore if they were described.
Clearing the count becomes the objective, and the tidiness itself supplies a small reward independent of whether anything mattered.
Recovery costs more than the interruption
The visible cost of an alert is the seconds spent on it. The larger cost is the time to rebuild whatever was being held in mind beforehand.
Work involving several pieces of context at once is most affected, since resuming means reassembling all of them rather than picking up a thread.
This is why frequent short interruptions degrade complex work far more than their total duration suggests.
Defaults matter more than settings
Almost every application requests permission to send alerts on installation, and the request arrives before the user knows what will be sent.
Operating systems have added controls in response, including scheduled quiet periods and per-application limits, and they work well for the people who configure them.
The durable point is that the effective defence is structural rather than behavioural: what is not delivered cannot be resisted or failed to resist.