Maturing quickly would be a wonderful trait for a hostile environment, LOAF, but unfortunately it would also make any development of a civilisation an outright impossibility. The kids would consume so much (growing adolescents eat quite a bit... imagine how much someone growing at a rate some ten-twenty times faster would consume) that the entire clan would spend most of the day hunting and gathering just to keep the useless little brats alive. Thus, in order to have enough time for other things (weapon making, and other vital skills without which civilisation doesn't develop), they would limit the number of kids to a bare minimum. Ergo, the population wouldn't grow - and without population growth, there's no possibility of civilisational development, because there's nobody who could spend the whole day sitting on his ass thinking of what to do with his stone tools, those seeds and that empty plot of land. This in turn means that food production doesn't suddenly increase in leaps and bounds, and therefore the population can't grow. It's a nasty little closed circle.
A similar closed circle
has occured on our planet, in Australia. The Australian Aborigines have absolutely astounding arts and rituals, but they have no technology beyond boomerangs and spear throwers. The terrain they live in (well, most of them, since of course Australia is a vastly varied environment) is rather harsh, and they can't afford to have more children - so the population doesn't grow, and... well, I'm starting to repeat myself, but you get the drift. It's no coincidence that the densest populations in Australia were in places (the Murray River and Western Victoria) where the environment was... lenient... enough for them to be able to get food surpluses and spend the rest of the day thinking up better ways to get more food surpluses.
On Kilrah, of course, it wouldn't matter how lenient the environment was. Even if they lived in Paradise, these 'accelerated growth cubs' would consume about as much as ten, maybe fifteen adults. So, you'd need ten to fifteen adults working at twice their usual pace just to keep one cub alive. Who's gonna bother?
Wow... would you look at that. I really need to cut down on how much I write
.