No doubt true in the abstract. But when the thieves and killers are right outside your door the view tends, I believe, to take on a certain urgency and the next election cycle becomes far less important than simply ensuring you and your family can live unmolested.
The main problem with vigilante justice is that sometimes it is not just at all. The wrong fellow is strung up or a member or members of the vigilance group takes advantage of the situation to exact revenge on an enemy who committed no crime. Governments make the same mistakes and commit the same crimes but we entertain the hope that the process has enough oversight and accountability built in to keep such miscarriages to a minimum. But it should be pointed out that not all governments are equally rigorous in keeping the system upright.
If I lived in a country where police and courts are arbitrary, corrupt and generally unreliable I think I might be very much tempted to take matters into my own hands. And if others shared my concerns I would join with them. I would try and make things as just as possible and in some places that would be an improvement over the “justice” meted out by corrupt police, judges and government officials.
If I read history correctly societies will normally adhere to the rule of law IF the rule of law exists at all. Generally it seems that vigilantes crop up where government fails or is virtually non-existent. In those cases to appeal to the government is a waste of time and maybe even dangerous.