Comment by klyrs

Yes, because its catalog is also a CAD library, so you can put the parts into your design and be sure the parts will fit when they arrive tomorrow. Because every part is neatly categorized, searchable by its properties.

I am infuriated when shopping for clothes, computer parts, etc. because the items are rarely categorized and when they are, it isn't comprehensive so searches tend to miss out on the obvious so I end up browsing a site's entire catalog.

And, they do sell a lot. They're the industry standard. The only problem I've had is that they won't ship to individuals in Canada so I had to think up a fake company name.