I got that question so many times along all my social media.
The simplest answer is: It's not.
But here goes the reason why i won't take it out of any of the sets:
5 years ago a close relative was living in a European country and while waiting for the bus a man approached him to start a conversation. My relative is a very friendly guy, he can establish a good conversation about anything, anywhere. After sometime, this new guy offer him a beer from his backpack, my relative accepted it and the next thing he remembers is waking up in a hospital bed.
The doctor said that my relative was drugged and that he was lucky because if the beer had a bit more of "the substance" he could have died.
My relative was in his fifties and so involved in the conversation that he didn't paid attention that the bottle he received was opened already.
While drugged, he was robbed. Can you imagine if this happened to a woman? We are in a greater disadvantage from wherever point you see it.
A lot of you party and there is nothing wrong with going out, but if you like to drink from a bottle please make sure is closed. Sometimes even bartenders are part of the problem - not all of them but we never know who is there to protect us or who we have to protect us from.
If you don't currently own a bottle/can opener...don't worry, you will always find one in your self defense keychain to protect you and your friends.
Please party responsibly and open your own bottles or cans.