Why can't people of the UK get iTunes Radio?
Relax. You're not the only country. Most tv/video/music services from American companies start off as US only and eventually make it to lots of others like UK, Canada etc. in fact Apple has one of the better track records for just this. Take a look at how many countries the iTunes Store is in compared to google play and amazon. I'm in Canada and patiently waiting for iTunes Radio as well. I've become very accustom to waiting for things Americans already have. Apple said they're expanding it this year. I believe it's already made it's way to Australia.
Also, there's very legitimate reasons for why this happens. There's lots of legal/copyright things to do and deals to make. Btw, there are always unofficial workarounds but I'll leave those up to you to figure out (google it).
It has nothing to do with money. Apple would welcome the greater revenue but it's not a matter of money. I feel your pain though. In Canada we're right next door to the US and always end up waiting longer, paying more or not getting services/products at all. It's been like 5 years since Google said google voice is coming to canada. Pandora is still non existent here. Still waiting on Spotify. We've got Netflix but our library of content is a fraction of the US one. A lot of it has to do with the politics of the studios/record companies and the horrible copyright laws.
Again, many have resorted to DNS/VPN workarounds. Explore at your own risk as legality may vary in your country and I'm not even sure about the forum rules on discussing DNS/VPN workarounds. For iTunes Radio specifically I believe you don't even need to go that route. I think you just need a US iTunes account which is easy to get even if you're not in the US. Google it.