Typically those wiggles are for length matching on parallel busses. Since the signals are clocked at a high speed, ensuring all the bits arrive at the same time is crucial.
Differential pairs carry polar opposite signals so that any noise can be canceled out by comparing the two. While parallel bus traces need to be routed to 1/20-1/40th of a wavelength, the differential pairs need to be routed to within 20mils of each other with impedance controlled traces (which depends on distance to each other and other traces as well as material variability, hence the tight routing).