Because Boeing didn’t have the same issue Airbus did. The latches on A320 family cowlings were kinda hidden from view, which made them less likely to be seen during the pilot’s walk around before departure. The EASA (and then subsequently the FAA) issued an airworthiness directive [1] that required the visibility to be resolved. For this case, it’s simply both the mechanic forgetting to latch it properly _and_ the pilot missing that fact during the walk around. Either way, it’s not really a safety critical incident, just rather embarrassing. [1] https://www.federalregister.gov/documents/2017/06/29/2017-13...