Rooting cuttings in plain water?

[JerryHaskins]

I have seen folks root cuttings in plain water over the years.

But I have several books on plant propagation that discuss various rooting techniques---but none mention rooting in water.

Nor do any of the Youtube rooting videos I have watched mention rooting cuttings in water.

What I have seen is (mostly ladies) who took a cutting from a plant and stuck it in a glass or something filled with water and left it on the window sill.

Pretty soon there were lots of roots.

Then they stuck the rooted cutting in a pot.

Anybody know about how to do that or why it does not get discussed?

Just curious.

Thanks.