The staffing arithmetic rarely works and rarely gets stated. Covering nights and weekends properly takes more people than most estates can justify on volume, so what actually happens is an informal rota of the same two or three people, who are also the people the projects need. Nobody signed off that arrangement; it emerged, and it holds until one of them takes a holiday at the wrong time.
What degrades first is not availability but hygiene. Patching slips because the change window competes with a project. The asset inventory drifts because updating it is nobody’s ticket. Monitoring accumulates alerts that everyone has learned to ignore, which is worse than no monitoring because it produces the belief that something is being watched. None of these is an incident, and together they are the conditions for one.
Key-person concentration is the risk that nobody prices. One person understands the backup configuration, another is the only one who has ever recovered the identity platform, and the documentation for both is a mixture of out of date and absent. This is fine until it is not, and the trigger is usually mundane, a resignation, an illness, a promotion.
The out-of-hours experience is where the gap becomes visible to the business. Something breaks at eleven at night, and the honest answer is that it will be looked at in the morning, or that someone will be woken who has no runbook and no authority to make the decision the situation needs. The cost is not the outage duration; it is that the business learns not to rely on the estate.
The reason this persists is that fixing it looks like admitting something. Bringing in support reads internally as a judgement on the team, when the actual finding is almost always that a competent team is covering more surface than its headcount supports. That framing matters, because an engagement that arrives as a criticism does not work.