> I think it quite likely that said dispenser and many other components can be 3D printed in metalurgicaly perfect titainium and then subject to NDT ,while saving weight and money.
You'd still need to pay for the certification and audit trail paperwork, and in addition you'd take a part that has already been certified and replace it by a new one that would need to undergo the same certification requirement.
> weight is the enemy, the other is simplicity, : if its not there, it costs nothing, and cant break
Indeed but then you get crews taking their own soaps because they (think they) need to have soap aboard, store them wherever it is convenient for them, and the soap bar then gets loose and flies during the cockpit during a mission because no one thought about securing the soap as it isn't on any checklist.
That is also the reason why even brand new airplanes rolling off the factory line still have ashtrays in lavatories despite smoking being banned for decades now. They account for some dumbass thinking they do need to smoke and better they drop the cigarette in the ashtray (because that's what people do naturally) when the fire alarm goes off, than they dump it in the trash bin, causing the cigarette to set the trash alight and causing a bigger issue.
That is "fail-safe by design". Even if it adds 100 grams per plane to have that ashtray and a bit of work for the attendants to check if it needs to be cleaned out and for the pilots and maintenance crew a bit of work in the MEL check, it is still worth it over losing an aircraft due to a trash bin fire (and yes, that still happens, see the source for this quote!):
> As with just about everything on a plane, it's about safety. "They're there so if someone were to break the rules, they would dispose of the cigarette in the ashtray as opposed to, say, a trash bin full of flammables," says Robert Antolin, chief operating officer at App in the Air. [1]
[1] https://www.travelandleisure.com/why-airplanes-have-ashtrays...