In some cases, they'll determine your ability to get hired. In this process, logbooks might be more important than you think. If you're applying for a job in the cockpit, you're being hired not for the certificate you hold, but for the experiences and knowledge you've built over time that will make you a successful and safe professional pilot.
They're a representation of you as a pilot, your personality, and your skill sets. Logbooks aren't just a way to keep a track of your flight times and training records.