The line is made at any time, may ignore for pub. However, it is considered rude if you obtain services from employees who know that there are people waiting.
The line is to practice all the time. May be omitted for the pub, however, considered impolite if you receive services from employees who know that there are people waiting already.
The line is to practice all the time. May be omitted for the pub. However, considered rude if you receive service from the staff knowing there's one before.