The basic gist is that blue light is much more scattered than other colors. Thus, by polarizing (i.e., filtering) the blue light, you are providing some organization to the scatter of light and thus increasing its purity or saturated-look.
But now comes my take on it all.
I very rarely encounter scenes where I can or want to reduce the surface reflection of water. It’s happened maybe 2 or 3 times in my entire career, to be frank. Thus, that’s not the draw for me. Most of the time I’m actually trying to get the reflection on a lake or pond to mirror the mountains, or clouds, or trees, or whatever.
I love saturated blue skies as much as the next guy. However, there’s one big problem with using the polarizer to do this. Once you take the photo with a filter on your camera, yielding very saturated skies, it’s difficult to removethis effect, should you not want so much saturation. On the other hand, it’s relatively easy to increase the saturation of skies on an under-saturated photo via photo editing software. Therefore, I find that you are really committing when you use a polarizer, such that you must know you want a heavily saturated blue sky before you even have the chance to review the photo on your computer.