The gsconnect add-on is installed for GNOME in the full version, but it should be enabled by default, since most users have a compatible smartphone (and they mostly don’t know about it).
If you think most users don’t know about it, what’s the point in enabling by default?
Enabled extensions are kept to a minimum for a more stable and lean experience out of the box. GNU/Linux is about freedom and choice, not forcing things on others and/or assuming what they want.
I don’t think it’s a good idea to have programs and services launched at start up by default that not everyone is going to use. And not everyone has an Android device.