You get tracking with Ground Advantage also, at less cost and usually with the same delivery time as Priority Mail.  Stop wasting your clients' money.

For incoming mail:  A client mailed me a package from a suburb, 25 miles from my office, and it took nine days to arrive.  But the address was hand-written in light ink on a grey envelope.  The Post Office sorts packages with scanning, and most addresses are recognized.  If it has to get past human eyes, several times, it goes very slowly.  

For outgoing mail:  You people are living in the era of long-distance charges.  "I made a phone call to Montana, why didn't it cost more than a local call?"  Well, that's just the way it is in the 21st Century.  Your mail goes from a local collection office, to a regional distribution center, to another regional distribution center, to a local delivery office.  Most of the time, between distribution centers it's on an airplane.  That's not where the time is spent.  It's on the ground at several sorting locations, where time is required.  

Even local mail travels farther than you think.  Mail something in Tucson, even to another Tucson address, and it is brought to Phoenix, 120 miles away, for sorting.  Then it is shipped back to Tucson.