Almost all of the testing I've managed has proven that content delivered via carousels are missed by most users. Few interact with them and many comment that they look like adverts — we've witnessed the banner blindness concept in full effect.

In terms of space saving and content promotion, a lot of competing messages get delivered in a single position that can lead to focus being lost.

I'm quite certain that they are indeed a user-interface cliché borne out of their inclusion in wire-framing apps and being part of JavaScript frameworks.