Toolbars have text labels. Ribbons have a bunch of small shitty icons on a flat UI background. I can memorize toolbars because it's a set of motions, words, and visual cues. With a Ribbon UI it's a mad search for what I want, hovering over dumb icons to see a label, and repeating that process until I find something. The damn search and rescue process totally blows away my working memory and I won't remember where the button is next time I need it.