I'm betting the other stations do have the networked capability to access, print, and hand
out Main Trail permits, just like other trails. However, limiting Main Trail permits to the station in Lone Pine likely has more to do with the Lone Pine rangers' familiarity with Whitney (which rangers in other areas may not have), which would also relate to the pre-hike checklist the Lone Pine rangers go through with everyone picking up their permits. Many people hiking Whitney for the first time will, no doubt, have questions resulting from going through this pre-hike checklist; the familiarity of the Lone Pine rangers with Whitney will allow them to better address those questions than rangers in other areas.