I don't think boroilicate glass is as perfectly pure/clean and safe as most simplistically assume. But in practical applications (like mass market vapes), it's often the most 'pure,' 'clean, 'safe,' etc. option.
Glass by definition is a very complex mixture, far from pure, unlike say actual pure quartz/silica. Related to this, glass is very rarely used in biopharmaceutical manufacturing, it leaches too much diverse substances into fluids it's in contact with, with bioreactors, chromatography columns, filter housings, piping, etc., particularly product contact surfaces, being composed of stainless steel or inert laminated plastics that leach much less. High quality borosilicate glass is commonly used for chemical reactions and manufacturing where this generally works well, with clarity, being able to see what's happening, a major advantage here (and also with vaping). Glass used with some analytical equipment, where genuine inertness is needed, is often silanized, coated with a layer of silicone (although silicone a complex mixture of different size polymers and unreacted silicone); or PFA is used.
Physically, glass is inherently brittle and prone to spallation/delamination, with exposed surfaces shedding small flakes. This is a persistent problem in the pharmaceutical industry, such as with injectable drugs filled into borosilicate glass vials. For example, see
https://www.corning.com/worldwide/e...ologies/pharma-technologies-delamination.html and
https://www.pharmtech.com/view/causes-and-implications-glass-delamination.
If you want solidity/physical integrity, ability to handle rapid heating and cooling, non-leaching, purity, and biological and chemical inertness, pure pharmaceutical grade silica/quartz, PTFE (Teflon) and PFA plastics, some metals (titanium, silver, copper), some ceramics, and some forms of pure carbon (diamond, graphite) may be better candidates.
Diamond is the most chemically and biologically inert material. Diamond-coated vape air flow contact surfaces might be ideal.