Earlier quoted context omitted.
Companies are being as picky as they can get away with.
It’s weird seeing the same posting I got rejected for 6 months later. Surely work needs to start sometime?
Even if it's not "market research" position (to assess how many relevant applicants will apply) it can be open by the HR at the request of prospective hiring manager because they would like to hire somebody at some point.
I helps businesses create an impression that they're growing (because they're hiring), gives HR some work to create impression they're busy and invaluable, and improve metrics of whatever job boards they post it to. Everybody wins.
I've seen the same positions open for more than a year and even applied for one like a year after I was rejected after an interview (just for fun). It was a different recruiting agency the second time and I think they submitted my resume again because I was pretty much perfect fit :-)