So...what IS it for? quote of the moment

 Your rectum is not designed to drink alcohol. It is sensitive and easily damaged. That is why you don't use your rectum in most daily activities or to operate heavy machinery. 

-- Bruce Lee

(For real.  Right here 

https://www.forbes.com/sites/brucelee/2018/09/29/what-exactly-is-boofing-and-why-you-should-never-do-it/)