Ending the show without a Season 5 allowed the creators to maintain narrative integrity. The final season is set two years after the events of Season 3, showing a broken Lucas Hood living in exile. It strips away the "fun" of the earlier seasons to deal with the trauma that the violence caused. It is a dark, brooding conclusion that grants the characters peace, but at a terrible cost.
Banshee is a show that respects its audience. It respects the genre. And most importantly, it respects its characters. It gave us four solid seasons of storytelling that never dipped in quality. how many episodes in banshee season 5