Over time, our teeth shift creating spacing and crowding where there may have been none. To resolve this we typically use orthodontics to straighten and then make retainers to hold the teeth in that position.
For people who don’t like flossing, I recommend a water pick. Honestly, a water pick is more beneficial than flossing. A water pick can reach far beyond the gum line than flossing, which can only get 1-2 mm below the gingival margin.
The bacteria that plaque consists of would cause the gum tissue to become inflamed and infected. The infection could spread to the jawbone and ultimately cause tooth loss.