It is very easy to contaminate glassware, and especially over time, if not rinsed in DI water and thoroughly washed, becomes tainted, and useless.
When I was a chemist, standard practice was, before any sample was tested, was to rinse the vial at minimum of 3 times with DI water, take the sample and test, then rinse 3 more times in DI water, and turn upside down.
At the end of the day, all glassware was washed in an acid based liquid.
Because DI water is so devoid of any components, it has the ability to remove deposits from the vials.
My bet is.....this is what the chemists do at the Las Vegas water authority.