The FCC requires a log of all international contacts
The FCC requires a log of all international third-party traffic
The log provides evidence of operation needed to renew a license without retest
To help with a reply if the FCC requests information about your station✓Bonne réponse
Explication
The FCC dropped its amateur logging requirement decades ago, so a log today is voluntary. Its practical value is having a contemporaneous record of your operation to draw on if the FCC ever asks about it, alongside award and QSL tracking.