The problem really is that more and more operators are trying to save as much as possible by releasing flights with minimum fuel and addition to the shortest alternate in good weather conditions. Of course what was said above about being committed at your B destination after a go-around is the correct action but I raise you this..
What if in a nice CAVOK day your destination B is a very busy airport and you just have fuel for the shortest alternate and you got unexpected hold due traffic and then when committed to your B airport the aircraft in front of you crash-lands and you have to go-around? .. or what if this happens as you hold and ALL the traffic starts diverting to the shortest alternate, the same alternate that you have and you can barely reach? This is exactly why I m not so fond of minimum fuel flying in CAVOK conditions. The emergency extra 30 min of fuel is always something you can use but you re going to loose at least 10 years from your life if you land on fuel vapour..