Why does it seem like most Matched Betting is in the UK?

I've been reviewing and researching matched betting for about an hour or so because it seems like an interesting concept. But why does it seem like most of it is in the UK? I can't find any answers to this question.

Thank you.

2016-04-27T13:10:58Z

...Most online gambling is illegal in the U.S. I see...
Well, I found it.

?2016-04-28T14:39:41Z

The British, like the Chinese don't have a hang up over gambling, the American States will promote shooting and killing each other, via the 2nd amendment, but don't like having a flutter on something, and many ban gambling and Casinos.

I live in the North of England, the local large City is Leeds there are at least three Casinos open 24 hours a day, to say nothing of Sheffield 40 miles down the road with at least 4 all day Casinos, Manchester with 6, and a betting shop (Book Makers) on every row of shops in every district of every Town and City, probably 50 to a 100 in Leeds?