In reply to calm.

Hey calm,

You are right, this is a problem that should be solved in core. However, solving it in core will only work if every plugin adheres to the standards defined by the core. As this is highly unlikely to say the least, there will always be heaps of plugins that use attachments that would not be detected by such a core feature. This is where Remove Unused Media shines, as it does not rely on any standard way of including attachments. Unlike your assumption, it does not just search the database but checks the generated HTML as well. It checks portions of the database, the generated HTML as well as some special locations to find as many media usages as possible without false positives or taking hours. An actual real time solution is in the works.
Checking the webserver log does not work in many cases. Imagine a post that is rarely viewed, the included media files would be marked unused and get deleted.

Storage is cheap, but speed and time are invaluable. A cluttered website reduces productivity and speed. True, for most people the ROI of Remove Unused Media is not measurable, but once a site reaches a certain size cleaning up becomes a necessity, and this plugin saves you a lot of time and makes it much easier and less error-prone to do a real clean-up.

Greetings from the Remove Unused Media team,
Jonas