This question is part of the following Ask The Expert session:
You are right in a perfect world and the best thing would be to not use antibiotics at all. Some might need antibiotics if their equipment or air-handling systems are not perfect. Some might use certain antibiotics for selection. Others might use antibiotics during primary culture. Sometimes it might be necessary, but if possible I try to do without it. If you are learning cell culture I strongly recommend not using antibiotics so that you can learn good technique quickly and not develop bad habits that may be masked by antibiotic use.