Imagine you are developing a long running service in Java (most likely you already have one) and found a bug in production at some point, how can you identify the root cause of the bug? The answer is simple: analyze your logs. If you already had your logs written to a file you are in a good position. If not, you may have to rely on the mercy of Docker container logs (if your service is containerized) or else you are doomed.
Even if you have logs appended to a log file, you must consider rolling log files to keep them small and concise. If not, be prepared to open a megabyte/gigabyte size file with millions of lines and find a needle in a haystack. Enabling rolling file log in your application is not a big deal if you know the configuration. However finding the right configuration every time you need it requires a lot of web surfing.