I learned cursive, then reverted to print, but when I entered a phase of my life where I needed to write several pages a day I quickly went back to (a custom variant of) cursive because it was faster to write in a legible way than print.

When I rush print it quickly becomes illegible. When I rush my cursive it doesn't look quite as nice as it does when I'm writing steadily, but I can still read what I wrote ten years later.

From what I can tell it works because cursive letters are defined in a shape that lends itself to a quick moving pen. Once you learn that shape (both to write and read), you can quickly get words down on a page and then understand them later. If you just try to slur your print in an unprincipled way your letters distort in ways that make them harder to tell apart.

Now, I imagine someone could develop a slurred print that doesn't have connections between letters, but I'd probably call that a cursive anyway.

Later I found out it was developed for use with a fountain pen, designed with the idea that a correctly-faced nib would make some strokes bolder and others very faint, and to keep the nib always moving in a kind of flow to avoid spots, and to make it natural to keep the nib faced the correct way(s), plus with even more attention to avoiding raising the pen than most cursives, for similar reasons of avoiding spotting. That made all the downsides make sense—it's far less ugly and easier to read when written with a fountain pen, and may well be faster than many other similarly-clean methods of writing with one.

Why the hell we were still learning that hand decades into the dominance of the ballpoint, remains a question.