Why is Yahoo answers getting shut down ?

Because Verizon Media is choosing to shut it down (just as they did Yahoo Messenger and Yahoo Groups). No specific explanation was given, but considering the significant decline in quality of content on the site versus the cost of cleaning it up and keeping it running, it's not a surprise (a disappointment, but not a surprise). 

New laws are coming out that will hold social media sites responsible ( libel) to clean up what is posted ( racism. slander, abuse ,porn etc...FAST or face fines = $$$$$$$$$$$

It's supposedly decreasing in popularity. I myself used to visit Yahoo Answers often, but not as much in the past 2 years.