Probably just more mental overhead people don't want to deal with. No one wants to remember to do more stuff. If you're comparing 2 trucks, one with a DEF syst

Probably just more mental overhead people don't want to deal with. No one wants to remember to do more stuff. If you're comparing 2 trucks, one with a DEF system and one without, chances are as an average consumer, you're going to take the one without because it's cheaper to run and less effort for you. Heck, the other day I was looking at some electronics on a very large Chinese shopping site and ran across a device that can emulate DEF systems in 8 different manufacturers vehicles with no actual DEF consumption occurring for ~$15. People are lazy, cheap and just don't give a shit.