According to the CBOT, the YM continues to become more popular and is setting open interest records. While the YM may never be as popular as the ES, I don't see why that matters to the small retail trader. You can do a 20 lot at any time on a Bid/Ask that is rarely more than 2 points wide and is often 1 point wide. Doing 50+ is not a problem if you go two deep. For the small trader, that is perfectly suitable. Also, I happen to know that the CBOE MMs often hedge SPX with YM instead of ES. nitro
Because it takes alot of movement away from the S&P so either it goes away or it starts to do something. Anything but what it currently does which is nothing. The arbs make sure nothing moves without it. Afterhours YM are just a cancer on the rest of the markets. Market is just an abortion.
Actually these have some utility - I have traded these a bit successfully although by no means am I any expert . I dont see any reason why these will be going away, especially if people continue to use them.