This is a bit of an exaggeration.

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.