Also if they fixed their website they could really hurt McMaster. They overlap in most areas; in fact if it were more reasonable to search things like raw materials we might all be surprised at how much is available to us through Zoro.
edit: yes, I understand Grainger's site can be used. As a business operating a separate website, that's hardly the point, is it? If you worked in IT and told your boss, "It's ok our website is mediocre on a good day, customers can just find part numbers on our sister website," how long would you expect to have a job?
The saddest thing is that Zoro's search has gotten better over the past 3 years, but it's still cumbersome at best.