Cant understand why they insist on taking the lids...

Cant understand why they insist on taking the lids off any bottle you buy...arena rules they said....safety they said. The water coke and beer that was spilt by the end of a buble concert meant the policy had now given rise to an avoidable unsafe environment.....Why? Its also really easy for anyone to drop something in your bottle without you realising....must be hard clearing up at night with all those half empty bottles and no lids....had to leave the bottle there rather than use it on the journey home, what a waste.