A proper assessment at the start of a coaching relationship changes what you programme, not just what you know about a client, which is why it is worth the extra time it takes.
Here is what a useful assessment actually covers, and why skipping it tends to cost more time later than it saves at the start.
A movement limitation or an old injury spotted in an assessment can be designed around from day one. Found three weeks in, after it has already caused pain or a setback, it costs far more trust to work around.
Strength, mobility, and conditioning baselines turn "getting better" into something you can actually measure. Without a starting point, progress is a feeling. With one, it is a number you can both point to.
An assessment is the first time a client sees how you actually work, not just what you say in a sales conversation. Doing it well builds more trust in a single session than several weeks of good programming alone would.