Its a great way to get back at someone without causing any real danger. Depending on the brand, the glitter goes everywhere and is usually really annoying to remove from things like carpet. Also, if a laywer opens it, they're likely to charge the client their full rate while they have the cleaning done.
Bonus points if it leads to someone being accused of infidelity later on.
Its harmless, and annoying. But less annoying than being ghosted. I think its the correct way for an interviewee to show they care.