Serious answer: my sister has been pushing me to get one. But she introduced the concept to me with a bottle of tequila inside. The hangover the next day wasn't nice at all. I do have a question though as you seem more trustworthy than my sister 😭 can I stick them in the freezer should I need to make something cold quickly?
Not so serious answer: because I want to be a drunken master!
Freezing water will break insulated bottles but why would you put insulated anything in a freezer? You will not get anything cold quick by putting in a freezer in an insulated container
In Brazil we drink mate from cuias, but they're made of wood and so very hard to clean. First time I used one I cleaned it with soap and let it dry upside down on my counter, woke up to find it completely mouldy.