Perhaps it is there, but just so thin you don't see it?
I found this somewhere a while back and it helps greatly
with gtk scrollbars:
zooty> cat .config/gtk-3.0/gtk.css
.scrollbar {
-GtkScrollbar-has-backward-stepper: 1;
-GtkScrollbar-has-forward-stepper: 1;
-GtkRange-slider-width: 15;
-GtkRange-stepper-size: 20;
}
Scrollbar wide enough to see and arrows to
click on to move a small amount instead of
having long lists go zooming off the top or
bottom when you try to move the thumb.