I purchased a pair of wool hiking pants once, but found that I have only worn them a few times and don't really like them all that much. The worst part is they are not very easy to clean. You can get pretty dirty sometimes when you are hiking, and I want something that I can easily throw in the wash.
They are very warm, but I also found them to be too hot for me. When I hike, I would rather be too cool than too hot, and the wool pants were too hot for me. They were also a bit bulky, which made it a little uncomfortable too.
There are advantages to wool pants in certain situations, but I found that they just don't usually work best for me and the hikes I take. It is nice to have so many other choices of hiking pants to choose from though.