It's been brought to our attention that having syslog in core might be a usability problem. Almost all the other core modules are features that users can turn on, and play with. Syslog, on the other hand, requires some server configuration to get it working.
Syslog is great for hosting providers who already have support for system logs, but for the first-time user or small site owner it's very confusing to enable this module and have nothing happen, with no indication as to why not.
I'd love to get feedback from users, as well as hosts like Pantheon to see how they'd feel about moving this module to contrib.