Carrara needs a lot more or better features for modelling.  If you compare it overall to other apps, it holds up real well for the price, but if you really want something for more than rendering Poser stuff, then you find it is lacking in some really core features, like modelling tools.  Sure, you can model things in it, but it's not fun, and compared to something like Blender, it would take forever to model high poly objects in Carrara.  Carrara is cool, and can be fun, but for doing some real work, and creating scenes from scratch, with all your own models, it's kind of outdated.  Hey, that's just being honest.  I'm not trying to bash it, just being realistic.

I don't see many people creating really high quality models using only Carrara.  At least not on average that doesn't happen, and there's good reason for that.  Sure, some people probably do create some fantastic realistic models with it, but it's a rarity.  Hey, people actually still use Bryce for modelling some far out high detail models too, but it takes them months.