Since their business is to find an area hit by a storm, they quickly move in and do very fast work, taking advantage of insurance policies to cut costs. Consequently, doing very fast work with cheap materials leads to undesirable results. They use the cheapest materials and practices to quickly get a job done, leaving an unreliable, short term roof. A properly built roof can easily last a quarter century or longer, whereas a cheap roof thrown up by a Storm Chaser cannot guarantee a lifespan of even one decade.
Furthermore, since a Storm Chaser moves in, slaps on a roof and leaves, a homeowner will be unable to contact the roofing contractor should there be any issues with their cheaply replaced roof. The Storm Chaser will be long gone.
Storm Chasers also know the ins and outs of home insurance. They boast doing the job at almost no cost to the homeowner, advising them to take advantage of their home insurance policies, as well as offering to cover the deductible. Since insurance will cover the roof, (theoretically) Storm Chasers can entice a homeowner with the offer of replacing their entire roof, for FREE.