Crypto Trading 2017, page-1523

The winklevoss twins have been trying to get a ETF up for years  at one stage they were rejected

The brothers, made famous by their legal battle with former Harvard classmate Mark Zuckerberg over the founding of Facebook, previously tried to list a bitcoin ETF on an exchange now owned by CBOE. The SEC shot down that attempt, citing a lack of regulation in the bitcoin market, but the agency agreed to review the matter again.

https://qz.com/1044630/the-winklevo...coin-to-wall-street-with-a-cboe-futures-deal/

Its an interesting reason as  it essentially shows that the regulators expect and will only approve instruments that can be manipulated by forces other than supply and  demand