The US Senate banking committee wrote a letter to facebook questioning about the nature and legality of it's cryptocurrency project code named Libra.
https://www.banking.senate.gov/imo/media/doc/5.9.19%20Facebook%20Letter.pdfThey essentially asked whether it would enable users to have privacy and would make it harder for the government to monitor every personal and financial moves of people in the US and around the world.
of course, Facebook is a big fish they have not done it on other coins, they want to know since cryptocurrency is anonymous if they can still trace people purchase on Facebook services and products or it might avoid the IRS, judging from this, they want to protect the government income.