The Last of Us Part 1 needed to spend quite a bit of time exploring the Infected, not only in lore but also as an enemy faction. This is done gradually throughout the beginning of the game and the tension of Infected encounters in The Last of Us never truly dissipates because every level where a handful of runners or clickers need to be dealt with is suspenseful. Clickers are always a constant threat and shift the dynamic of gameplay drastically compared to when only a few runners need to be handled, and that threat is extrapolated when bloaters are debuted.