I see at least two advantages: speed and a consistent cross-platform interface. Unless you have a 10 gigabit LAN, browsing large media files over a home networ

I see at least two advantages: speed and a consistent cross-platform interface. Unless you have a 10 gigabit LAN, browsing large media files over a home network is slooooow. Having everything indexed allows you to do instantaneous searches of all of your files (with search tools / filters that may not exist in your native file explorer or would otherwise be extremely slow (Finder)), show instant previews, detect duplicates among all of your files from all of your storage locations, have a single authority for organizational systems like tags, etc. Offline is useful when you have a lot of external drives with contents scattered across them. You search for the file you want, it tells you what drive its on, you plug that drive in. This probably won't be extraordinarily useful to people who don't have a lot of network and/or detached drives or people who are meticulously organized and locked into a preferred solution already. But messy people with lots of data, devices, drives, and OSes? Pretty handy.