the appeal of kubricks, IMO, is that its shape draws from childhood toys like legos and etc but repackaged with properties from movies, video games, anime, comics, and such that are more familiar to current adults (it is suggested for 13+ on the package)
We all out grew legos at one point or another, and the reality is, most of us dont buy legos or playmobil once we out grew them. Doesn't mean that legos are not cool, the appeal is still there, its just not the same anymore. And this is where the kubrick come in, they are like a link to our childhood past. Its something that you buy not because you want to play with it like you did when you were a kid, but you buy it because it reminds you of the fun you had playing with legos and etc.
Sure, kids probably like them too, but for older customers, the kubricks are a more appealling purchase than buying legos. And the popularity of kubrick is a good indication that its not a lame concept.