Previous response by
@CanadaDrone :
Polarization is one effect that no post-processing software can reproduce, not even close in fact, so if you want that look the only way to get it is to use a physical polarizer. Polarizers can both enhance or remove reflections, so depending on the scenario you might want one or the other. For example if you were shooting a landscape with lots of foliage, you may want to take the reflections off the leaves - or the most common example, making water less reflective and more see-through. Sometimes though you want the reflection enhanced - for example a rainbow or if there is a nice sunset reflecting off some calm water.
If the filter is going on a drone, there is little value in an adjustable/rotating one because chances are you want maximum polarization if you are bothering to use a polarizing filter in the first place. Basically rotating it toggles the angle relative to the sun that receives maximum polarization, but it cannot magically produce a polarized effect at any angle - think of it more as changing the strength of polarization at any given orientation to the sun. It would also allow you to reduce the amount of polarization while flying in the direction of maximum polarization (90 degrees to the sun), but that would be something you would have to set on the ground anyway and there are far fewer scenarios where you only want a partial polarization. Whether you have a filter capable of rotating or not, you are bound to a single direction of flight if you don't want your footage to change mid-flight. At 180 degrees and 0 degrees to the sun there is no polarization. Maximum polarization is always at 90 degrees to the sun. If the sun is directly above you at high noon in an area near equator, you can get pretty broad polarization because most horizontal orientations will be roughly 90 degrees to the sun. If the sun is lower in the sky, there is a much tighter and less useful range that you will be able to achieve good polarization (basically straight up or straight down).
So let's say you were in Hawaii and wanted to get a nice shot over a coal reef, a polarizer would be great for that, you would just have to carefully plan the flight. If you wanted to fly in a different direction, you would need to bring the drone back home to adjust or remove the filter to avoid uneven footage. Or let's say you were hired to shoot some drone footage or photos of someone's car - you might want to completely remove the reflections in the freshly waxed paint by using a polarizer.
It's a good tool to have in the tool box, it just requires careful planning to get the most out of it and it's not something you want to just leave on and forget about like you can do with a standard ND filter. Most filter companies do a very poor job of explaining this to people and simply choose to market their PL filters as "vivid" or whatever, giving the customer the impression that they can just use them for any scenario and get better colors, which is far too simple and not the case.
