It's because your program probably depends upon other libraries, which all need to log their own info, and your life will be significantly easier if you can vie

It's because your program probably depends upon other libraries, which all need to log their own info, and your life will be significantly easier if you can view, save, and control logging from one centralized place at the top of your program. If every library rolled their own logging, configuration would be a huge mess, and your program would need to specify log files/formats/levels with each API call (or at least on API initialization). Logging facades like slf4j help a lot, but then you still need to implement the required interfaces. For something like the specific Log4J CVE, things would be significantly worse if it weren't centralized in a library. They have a bug in deserialization when talking to LDAP servers, allowing a compromised LDAP server to execute code remotely. It's likely that a subset of libraries would likely have rolled this functionality independently, and then you have many libraries that all need to be patched and updated instead of one.