This is exactly right. GNOME, KDE and other out-of-the-box solutions make sure to set the GTK and Qt themes so that everything looks pretty. When you use a WM (window manager) rather than a DE (desktop environment), it is up to you to setup all the ancillary things such as themes and daemons. This is why .xprofile exists!
Also, I find lxappearance an easy and quick way to set GTK themes via GUI rather than having to edit the .gtkrc files for every option.
Also, I find lxappearance an easy and quick way to set GTK themes via GUI rather than having to edit the .gtkrc files for every option.