Mtguide - I won't argue with you on the usefulness of USGS 7.5 Quads. It is true, they can be quite useful and I have numerous ones for sections/parts of ranges in Colorado, Utah, Arizona, California and other places where I have been climbing/hiking off trail or in areas that weren't covered on other, broader maps.
That being said, as a first time visitor to the southern Cascades, I will be climbing established routes and am looking for more of the broad overview maps that also show access roads, etc., and are updated more frequently then the USGS ones.
My argument was simply that I am surprised that there are no maps by Trails Illustrated for Mount Shasta and the southern Cascades (Three Sisters) given their popularity, particularly when the northern Cascades are covered so well by TI (Rainer, Baker, Crater Lake, Glacier, the Olympic Peninsula, etc.)