I do not know what is the problem with betting on players with underage games and what is the problem on betting on fixed matches.
The under age case is totally ridiculous nonsense. Indeed the restrictions will come, because the restrictors just restrict and since there is nothing at least a bit restrictable, it is all just a joke.
Obviously the only restriction that maybe makes sense is forbidding the underage betting, but even that is questionable for me. I was betting from my 14 years. Losing money I made with my own work. I was able to understand that this is really not the way to make money before I turned 18 actually. I was probably lucky because young brain is more flexible and can learn much better than old brain. Nothing is solved if people are allowed to gamble, use legal or illegal drugs or watch porn or have sex at certain age, when one day everything is grave sin and second day everything is allowed. In the past all sex/gambling/drugs restrictions were in place, but they were not heavily enforced and I believe it was much better way, because we all knew we should not do it, but we did it anyways and we at least had a chance to learn. Nowadays there is not such a grace period. I am sure - if the goal is to minimise the destruction - it is far the best from all the bad approaches to have laissez-faire approach. But indeed things went so far as Hitler to Moscow, so current trend is unstoppable until the liberals from cafes will be swept by alt-right movement and something even more ugly will appear.
As for the betting on fixed matches, I really see no problem. It is not paid from state budget. Anyone is free to watch price movements, anyone is free to make money on that (it is the last possibility nowadays to make money with betting and I know people who follow the price movements of [probably] mafia). Betting on fixed matches is like betting on stock market. Even at stock market is someone who has always insider info (yes, de iure it is forbidden). I think laws should solve some general problems and not a problem of betting companies. They should be able to profile players and restrict betting whenever they want/need.
If you talk to God, you are praying; If God talks to you, you have schizophrenia.