No way even if it's a huge amount, I will take the money but I will question the government and the organizations, it's going to be a big black eye for the lottery company if bettors find out that the government is taking 70% or even 60%, now people in that region knows that the government is going to rob them if they win a lottery.
Your argument will be invalid because like I mentioned few pages back, there's a term about the tax already. It's not the government's fault anymore if you are unaware of the withholding tax for big winnings. I understand that people might not be aware of it because hitting the jackpot is 000000000.1% chance so they won't bother reading the terms and just bet. The only time you can complain is if they won't follow what should be on the terms about the tax.
Why should they violate their own terms about the tax? It will just create a negative review about the lottery site.