In reply to Dheorl:
It depends on what time of year - if it's winter, most of the Cascades are seriously remote and challenging.
If it's summer, most of the cascades are just remote and challenging. A good chunk of the cascades are in the tree line (or at least the approaches are) and bushwhacking skills are important. Double boots will be ridiculous.
HOWEVER, it strikes me that by "the cascades" you actually mean Mt. Rainier. This is quite high and fairly Alpine. Like Mt Blanc, it can be quite interesting when the weather changes. Double boots would seem overkill, but yes, this is the American way of doing things. Particularly if it's a guided trip, in which case they don't want the clients having any risk at all of frostbite.
Also, being guided, they will want to "push on" if the weather is bad so that you are convinced you should have turned round earlier and again, won't want your money back. Rainier doesn't have too much in the way of objective dangers by the ordinary routes. Weather is the biggy.