Pulley lines are necessary when you need to run the line over a place you can't walk on. They're the main method used between tall buildings if the landlords agree to the reciprocal permissions, and might have some use for people who want a garden under the line or have some other obstruction.

They've NEVER been common in my area, because the weather (mustly the sun exposure?) rots any kind of flexible ropes so fast it's not worth putting one up except when there's a good reason for it.

Here, solid wire is the rule, with either two or (usually) three wires strung between "T-posts" that are commonly made out of worn out well-casing pipe.

A few people with very small yards have used "pivot wheel" lines, but they generally only last a couple of years before being abandoned in favor of a gas/electric indoor dryer.

Most newer "developments" in the immediate area have zoning or "covenant" rules that prohibit any kind of outdoor clothesline - but that's sort of a different matter.

And opinions not withstanding, birds CAN AND DO shit on the same line they're sitting on. (But maybe some places have clumsy birds that can't perform to the same athletic standards as ours.)

John