Because Objective-C is far from being an horror language, but perhaps your impression (and so mine) is conditioned by your past experience with your languages of choice.
I'm probably being unfair, I've never actually done any development in Objective-C (I have in C++), so I'm going on how it "looks" from the code I've seen, I just find it very unreadable. But in fairness I haven't tried to get into it, and I'm probably biased toward the C#/Java style syntax...
Cocoa is an incredible API. Much more pleasant to work with than Qt, hands down.
The runtime method dispatch of Objective-C (protocols!) makes it possible. Basically Objective-C gives you what Qt had to kludge in with qmake/moc. And it's still pretty fast!
When I see how little code I have to write to do something basic in Cocoa/Obj-C, and how well it turns out, any problems I have with syntax go out with the window.
Your initial reaction to Obj-C is not at all uncommon amongst developers used to C++/Java/C#. My impression is that most of them quite like it once they get past the novelty.
As a counterpoint I've written ObjC code for over 5 years for Mac OS X and iOS, and I'm not a fan. Sure it's better than C++, but that should be in the dictionary under "damning with faint praise". Header files, primitive types, and reliance on raw pointers should have gone out 10 years ago. The kicker was when I switched to Android development last year; when a language makes Java look comparatively elegant and concise, that's not a good sign.
I neglected to give more than a cursory glance at Obj-C back when the iPhone 3G and app store first came out. I hugely regret it now, but I was doing C++ at the time and thought it was the cat's pajamas.
If you can think abstractly and use/like languages like Ruby and Lisp (and their reflection/metaprogramming features), I think you'll be surprised by the amount of stuff you can do at runtime in native code. I started doing Obj-C a week ago and am about to submit my first free, 90% custom-drawn control app to Apple for approval.
Yes, the syntax is initially unappealing, but you get over it after about a day. On top of that, Xcode + Interface Builder is the best GUI dev environment I've used yet.
