Currently Blender shows all available add-ons by default. Furthermore, the chosen filter is not saved as part of the preferences, so every time Blender is restarted it defaults to showing all add-ons. Although this makes it easier for the user to discover new add-ons, it does make it harder to find and use the add-ons they have activated.
I suspect that most users activate the add-ons that they want to use, and then just use them repeatedly. By having the add-ons list filter on 'Enabled' by default, this becomes easier, especially for add-ons like the Blender Cloud add-on that heavily rely on the preferences panels.