3 posible answers Ringz,
* Anime studios are imbeciles
* Warning alert for moe overdoses (imagine the pokemon incident but with moe nukos)
* The author doesn't want this made anime (like the issue with Yotsubato)
Anyway, let me give you my best opinion:
This manga, even if moe, was firstly made as a seinen and sadly seinen manga don't usually respect their seinen style when turned into anime (have Umaru as example). If they make an anime of this manga but screw the heartwarmth of the series just for 100% more moe and fun, i'mnot watching