I suppose it depends on how anxious you appear. Its a sedative so its to relax you. I had them for operations under a spinal anaesthetic but not for generals.
Only reason I ask is because I have had 3 general anaesthetics and every time all the others in the ward were given one but I wasn't. I asked a nurse and she just smiled and said " I don't think you need one !" but she didn't say why. It's puzzled me ever since !