The short answer
Why measurement should be part of the experience architecture, not an analytics layer added at the end.
The interface creates the signal
Every interactive system defines what a person can see, choose and do. It therefore defines which behaviour becomes observable. Measurement is partly a design problem.
If interaction is ambiguous, the data inherits that ambiguity. A clean event log cannot rescue a poorly defined task.
Instrument only what matters
Useful instrumentation begins with a small event vocabulary connected to the brief: exposure, attempt, choice, completion, error, latency or return.
More telemetry can increase cost, privacy exposure and interpretive noise without improving the decision.
Design for failure states
Real environments contain queues, poor lighting, unstable networks, unfamiliar users and hardware variation. A measurable experience needs fallbacks and a way to distinguish behaviour from system failure.
The strongest systems make that distinction visible from the beginning.