I recently moved to England and was somewhat surprised to learn that gambling winnings are not taxed. A Google search reveals this article from Forbes that explains that such a tax would be at most revenue neutral. According to the author, the UK would want also to give tax credits for losses. Then since the bookies take a slice, there will be more losses than winnings, hence more credits than taxes, and the government will lose money on the whole.
One obvious objection is that tax policy is up to the government, and rates can presumably be tuned so that credits for losses are not as substantial as the taxes on gains.
It is interesting that the article focuses on spread betting in the financial industry and its parallels to more traditional forms of gambling like horse racing and poker playing. I am wondering if the real reason that gambling winnings are not taxed is to make the UK more attractive to the financial industry, so that the capital gains tax rate here can be offset by spread betting?