Maybe Canon introduce new technology faster so pro need every bit possible to win the next guy?
1987 adopting full electronics lens system with motor in the camera body to drive the mechanics against less precise mechanical lens and Nikon introduced their first G lens in 2000 (13yrs).
1987 (USM) first appeared with the introduction of the EF 300 mm f/2.8L USM lens, Nikon introduce SWM in 1998 (11yrs).
1995's incorporated IS in their 75–300 mm f/4–5.6 IS USM while Nikon have their first VR in 2000 (5yrs).
Canon moving into CMOS in 2000 Nikon started using CMOS in year 2007.
Canon offer full frame DSLR in 2004 while Nikon offer their first in 2007.