Comment by ryandrake
Recent Linux distributions are quickly catching up to Windows and macOS. Do a fresh install of your favorite distribution and then use 'ps' to look at what's running. Dozens of processes doing who knows what? They're probably not pegging your CPU at 100%, which is good, but it seems that gone are the days when you could turn on your computer and it was truly idle until you commanded it to actually do something. That's a special use case now, I suppose.
IME on Linux the only things that use random CPU while idle are web browsers. Otherwise, there's dbus and NetworkManager and bluez and oomd and stuff, but most processes have a fraction of a second used CPU over months. If they're not using CPU, they'll presumably swap out if needed, so they're using ~nothing.