Vertical storage carousels cover two different problems that both get solved by going up instead of out. Long stock, bar stock, sheet goods, lumber, pipe, panel material, eats up a warehouse's worth of floor space when it's stored flat or leaned against a wall. Stood up vertically in a rack sized to the material, that same stock fits in a fraction of the footprint, with each slot accessible on its own instead of digging through a stack.
The rotating side of the category, pan carousels and bar stock carousels, replaces the walk with a button press. Instead of an operator walking the aisle to a fixed location, the carousel brings the loaded bin, pan, or rack to the pick point. Powered turntables handle load rotation on a fixed footprint rather than storage, and a dedicated hospital bedlift covers vertical storage for healthcare facility equipment. What the whole category shares: manual vertical racks trade rotation for lower cost and simplicity, powered carousels trade cost for throughput.