Because static electricity is generated whenever objects touch, whenever wind touches an object, etc. Normally some objects can dissipate the charge if they ar

Because static electricity is generated whenever objects touch, whenever wind touches an object, etc. Normally some objects can dissipate the charge if they are conductive (for example a tree). But many man made objects do not conduct at all or are isolated from ground (for example car is isolated through non-conductive tires). For these objects, humid air helps slowly dissipate the charge, but when humidity is below 30% this dissipation becomes very slow process and a large amounts of charge can accumulate. I have home electronics lab and I keep a humidifier and ionizer to provide humidity and ions to dissipate any charges that can accumulate on any objects (like me).