Why? Selling is a normal part of any market - new supply needs to be absorbed, and that is normal and healthy.

The multipools aren't mining this because they probably have enough tech support headaches as it is, without being responsible for a mining client that merges this in with everything else they mine. Whether or not we'll see a multipool merge it in, I am not offering an opinion as such - I do believe it's possible we will see that, but I also think there are barriers to them doing so and there are easier fish to fry.