Why do many amateurs keep a station log?

While the FCC used to require all amateur radio operators to maintain a detailed log of every transmission, that strict requirement was eliminated years ago. Today, logging is generally optional for routine operations. However, maintaining a station log is still highly recommended as a best practice. The primary regulatory reason to keep a log today is to protect yourself in case of an interference complaint or an official FCC inquiry. Having a detailed record allows you to prove exactly when you were—or were not—transmitting, and with what equipment. Other answers might sound plausible, but the FCC does not require logging for international contacts or third-party traffic, nor do you need to submit a log to renew your license.