You may be interested in an answer I gave here previously. There is no real "why" answer - fashion simply doesn't tend to work that way. Cloaks used more fabric, but sleeved garments - like the greatcoat that replaced it for men, and the spencer/pelisse/paletot/overcoat for women - certainly required more labor to create. But once the sleeved option gained more traction in the late 18th/early 19th century, it became (as stated in that post) "the ordinary choice"; the cloak continued to be worn as an "unmarked" layering option by women through the end of the 19th century, but by the middle of the century an unsleeved cloak was a formal and somewhat unusual option for men. It's most likely that this ties into the tendency in the late 18th/early 19th centuries for men to eschew sartorial choices that had previously been seen as gender-neutral, but were newly considered feminine: it was acceptable if you were in opera dress or military uniform, but otherwise odd.

Does the cloak become "unfashionable" when it's relegated to the most formal evening opera dress only worn by the wealthy in the early 20th century? Technically, that's high fashion, but it's certainly far from the 18th century context where a cloak was just another layer to keep out the cold. Or is the cloak really only "out" in a period where the first thing people think of with regard to it is "kook dressing up" instead of "fancy opera-goer"? And it has to be said that garments like the greatcoat/ulster could have a relatively long cloak layer hanging over the sleeves (sometimes this sort of garment is even called a cloak in period sources), so it's hard to draw a line and say "it was fashionable here, and then it just stopped being worn."