On Tue, May 12, 2015 at 2:59 PM Stephen Gallagher <firstname.lastname@example.org
I think you'll find that
it's very likely that more users have installed the
Alternate Tab extension than are using the default behavior
It's worth noting that this particular extension does very little - it simply changes the default behavior of some shortcuts. So if you are implying here that something like the window switcher (in contrast to the default app switcher) should be built-in and not require any extensions - that's already the case.
You can reconfigure the <alt>tab/<super>tab keybindings using
gsettings set org.gnome.desktop.wm.keybindings switch-applications ''
gsettings set org.gnome.desktop.wm.keybindings switch-windows '["<Alt>Tab","<Super>Tab"]'
(or by clicking around in the appropriate section in gnome-control-center ...)