A case where it can matter is when there is no clear commitment yet to use that API.
For instance if there is 2 or 3 alternative services, and you want to explore one of them to have a better idea of the trade-offs. Setting up an account and making “real” requests will be your benchmark.
Actually, even for a service with a decent chance to commit to it, there will still be an exploration phase to get an estimate for the implementation cost. Depending on how much the devs struggle to just try the API, the project could get more or less reprioritized for lower hanging fruits.
For instance if there is 2 or 3 alternative services, and you want to explore one of them to have a better idea of the trade-offs. Setting up an account and making “real” requests will be your benchmark.
Actually, even for a service with a decent chance to commit to it, there will still be an exploration phase to get an estimate for the implementation cost. Depending on how much the devs struggle to just try the API, the project could get more or less reprioritized for lower hanging fruits.