Technological advances in their cameras. User reviews of their products. They have so many useful of lenses of different varieties such as the 24-85mm. So if it is lenses you want, Canon is the way to go. Their lenses are right up there with the quality of Nikon too.
Good lenses cost a lot of money.
Unfortunately, there are quite of few Canon lenses that are costly for fast glass like the 50mm f1.0. The is only a disadvantage to those on a budget. Not all lenses are compatible fully with different bodies. Lenses are reasonably priced for what they are. Camera bodies have an average turnaround of 5 years before replacement.