>>718539464
It's old dragon tech. Pretty much all the super advanced phogiston tech that the characters use is created by finding old dragon tech in some ancient ruins, modifying them, splicing together into something different and giving them a new paint job. The reason it's not common in Natlan is because dragon tech in itself isn't common. Xilonen can only create new gizmos by using old dragon relics.
For instance, let's say that someone took the hyper-advanced bullshit tech in Stormterror's Lair and fashioned it into a microwave. Or, fuck, take apart one of those Khaenri'an robots and turned them into a car. Would you still be complaining? The tech exists already, you just need to take advantage of it. Problem is, Mondstadt doesn't have any engineers. But you know who DOES grave rob ancient ruins and fashion them into high-tech weapons? The desert dwellers in Sumeru. They're not as good at it as Xilonen, but there's ancient tech all over the desert just waiting to be used. Kaveh created his briefcase using that very same tech. He didn't create it from scratch, it's just one of Deshret's machines modified into a briefcase.