They can however, police properly and immediately arrest those responsible to set the standard.They can’t stop bottles being thrown to be honest.
There seems to be a real regression of the way people behave in general in recent years.
In Germany I've seen two separate incidents of people getting slightly out of hand.
One got arrested and carted away to the cells, and another ejected by stewards right off the bat.
The key is to be proactive, sadly something we're not capable of despite cctv everywhere and plenty of cops and stewards about.