Another reason is that darkcoin focuses on its anonymity, while that all sounds cool, for mainstream, it would be very hard to get accepted because it's use would be seen as malicious because honestly, who needs to hide their money transfer THAT MUCH? Those who wants to do bad thing.
Basically, this is a coin that is the best replacement for scrypt.
all good, but clone are not seen well, and this is just a clone...
darkcoin is not a clone of anything, there was no other coin using x11
Also, ultracoin performs better than yacoin, which was the first with scrypt-jane