In my country those stadiums are just a money transfer schemes from public pockets via local government to local pockets. They have no problem building "temporary" stadiums while the old ones are "renovated" for hundreds of millions of dollars of tax payer's money. You cannot normally even visit the stadiums when there's no match being played. As you said, they usually need hundreds of riot police present each time because there is almost always vandalism and fighting. Those stadiums are not used for anything else. For example, I cannot ask the soccer team if I could use the pitch for say a day because I want to organize a drone racing competition. I would be laughed out of the room. As the other posters said, they just take my money and give it to some other persons who are living very luxurious. I know, Ferraris are expensive.

However, I understand that those sport events are like a safety valve on a pressure cooker. It lets those aggressive members of the community to vent so they don't realize how fucked they are in their daily lives. It something like a pacifier for those people. It is bread and circuses, and the bread is getting smaller and smaller.

That said, if the local government is spending money on (pretty much private) stadiums, then I would postulate that they have too much money and the taxes are too high.