As far as I can tell, most of the coins Bittrex delists are due to various USA regulations, not the actual coin itself. That being said, I personally believe that many of these delistings are good buying opportunities and have very real potential for long term holders.

Because Bittrex is a USA based exchange, they have the SEC to deal with. As. Of late, it seems that regulations have really increased. Research SEC and crypto currency, there is plenty of info published.