Surely one of the problems ...
is Microsofts total and utter lack of any track record in backing their OWN products. Their attempts at the mobile market is littered with the corpses of abandoned operating systems.
And all the apps that ran on them.
Much as I like Windows Phone (I do) I can't blame anybody for not wanting to waste their efforts on providing an app which might not last till the end of the year.
The most annoying thing, is Google are pretty much the same. I hope anybody pre-KitKat isn't too dependent on SMS blocking, since it's just disappeared with KitKat. Leading to loads of "SMS blocking apps" in the Play Store which don't - not that you'd know from the description.