As David explained, it is
tempered glass which is tougher; however, it
does break into safer granules, which is safer than jagged shards.
Laminated safety glass (two layers of glass with a plastic layer between them) is intended to hold together, instead of shattering into any size; that is another way to keep people from being injured by the broken glass, and it also makes the window better able to protect them from whatever nasty stuff might be hitting the vehicle.
Normally, laminated is used for windshields, and tempered for other automotive
windows.
Tempered glass is used for safety in sliding doors in buildings, because people tend to walk or
fall into them occasionally.
I agree that tempered automotive glass might help the durability of the trailer's
windows (for the reasons which Don and Byron mentioned), and it would be nice to have; however, with no risk of people walking into them, and no one in the trailer (in contrast to self-propelled RVs) during a potential collision, I don't see a need to
require this more expensive product. For security, laminated glass would be even better.
I don't know what the glass shop put in my
Boler window, but my guess is that it is neither tempered nor laminated.