Why would people pay for the taxes? it's the gambling operators that will pay taxes to the government, people are already losing money to these gambling operators, so that's even bigger than paying taxes, I don't get your point.
I agree, they should not impose the taxes to their users, they are making a lot of money, from their clients, they are the one should take the burden of the taxes, gambling sites are not selling products so they cannot add the taxes to their products.
The taxes that the government is imposing is for them to have a support coming from the government.