The truckers mast is designed - for two purposes 1. the 78"- 80" lift mast with lo or 0" free lift does not " generally present a danger of the load being tilted and falling backwards into the operators compartment or on his/her head & the fork carraige bars can serve as a load back rest. Of couse, there those " faux cowboys" or "NACAR driver wannabees" may want to try two loads high in one trip into the trailer. So what most manufacturers do - is request a letter of "indemnification" from the end-user to help protect them from PL suits when a truck is requesed (via written specifications) to be built & shipped without an LBRE & forks stops are provide on the carraige bar ends either by standard design or an approvided factory modification. After these fleet user retires these units after they have been very well used, they are sold into the second hand market hand are sold a few here & there - the seller should request a similar letter from their customer.
2. The other reason the large trucking companies use a truckers special mast is to reduce duce costs. Companies like Roadway, ABF ,etc. do not want to have closed van/trailers turning into a "sun roof" version - cost avoidance measure - they have a lot of those "cowboys & NASCAR driver wandabees"at their bulk break terminals. Of course, there are many more units sold with 189/83/ Full Free Triple or even up to a 89 -91" OAL triple (like a 216" lift) that are used to load & unload trailers (door openings of OTR trailers or containers can be 95" - 97" high) - but not in where roll-up doors are used or some 20' containers.