This is the number one reason patients have pain with their wisdom teeth. Due to the bad angulation, and spacing, it is near impossible to properly clean these teeth. Over time as enough bacteria buildup, the process of Periodontitis begins, just as in any other tooth, and you start forming periodontal abscesses, sometimes referred to as pericornitis. These can further turn into cysts, or much worse infections.
Due to the angle and angle of eruption, food traps can get created in between the wisdom tooth, and its neighbor. Over time this not only causes periodontal disease, but the inflammation in the area leads to large cavities forming on the roots of the adjacent teeth. Some of these can be saved, others however also need to be removed at the time of wisdom tooth extraction.
Due to the lack of space, when the wisdom teeth erupt, they can also force your front teeth together, destroying the years of work your orthodontist spent straitening your teeth.