reasons:
1. big and bulky, taking up the lane (and bike lane)
2. not driven by professionals, thus not used to wide turning radius etc
3. no accountability (I think) - if I call the company and complain, they're just going to say "gee sorry but those are not our drivers"

dimwit in a rented Ryder truck just about steamrolled me while turning through an intersection this morning. didn't even look.

and now that we're coming into moving season (esp. for students) there will be more of these numbskulls on the road.