Because China bans de skeleton. We can never have a ginormous skeletal king or some giant confligeration of bones as a champion. We will never have a Bone Golem monster in the game... that saddens me.
There WAS a skeletal champ http://lolwp.com/wp-content/uploads/Karthus-Classic.jpg however in china he looked like this http://i.imgur.com/4G37xeD.png
http://orig11.deviantart.net/97d8/f/2010/140/e/6/lol___karthus_fsjal_by_glodefunk.jpg still the best Beta icon
We can never have a ginormous skeletal king or some giant confligeration of bones
Jurassic 
?
We can't have a skeletal champion because they're too spoopy! https://media.giphy.com/media/FNnGlfxpLD36E/200.gif
To be honest though Karthus's newer design is far better than his old design. :o
The skeleton thing is a myth - Blizzard decided to proactively censor their game due to China's extremely vague foreign games policy forbidding superstition and living skeletons are something that weren't particularly offensive or anything but had a slight chance of being called superstitious as it gave the concept of death a physical representation. Other games only followed in Blizzard's stead because why the hell not.
Because Fuck China, thats why :(
Well China doesn't actually specifically ban skeletons, most companies in China just censor themselves and remove skeletons because of the slight chance that their skeletons in the context of the game would violate China's rules about religion and superstition, and thus get rejected, losing that company a fuckton of money. This usually happens for games that haven't been released yet, though.
So as far as LoL is concerned, there is a chance we could get a skeleton character. But they'd have to find a way to differentiate it from Karthus (As he used to be a skeleton) and Skeleton King (Or doom, or whatever his name is now. Damn Chinese censors :P) from Dota.
Sans is sad
all we have to do is go to war with China over them not letting us have skellies in vidya
We will also never have a skeleton skin for a champion :/
Given that inhuman skeletons seem to be ok,I'd say it would be actually possible for us to get an inhuman skeletal champ.
Like a dinosaur-skeleton,void-skeleton-monster or a skeletal dragon.
No HUMAN skeletons. Jurassic Cho'Gath exists.
I mean, do we really need a skeleton though? I like mutant zombies.
What's the issue with Skeletons anyway? We all have one inside of us for gods sake. Why not complain about Livers?
What about 
? I think blood is also banned in China.
China censors a bunch of unnecessary stuff. Get used to it
