> I suppose that a general-purpose, consumer-oriented site like Amazon doesn't put enough priority on something like M8 steel bolts. The facets for, say, computer monitors are much better, for example.

It goes beyond that. I was searching for a water pump this evening and hit Amazon out of instinct. Despite only returning 18 results across god-knows-how-many categories, there was no option to filter by manufacturer. Amazon simply doesn't get search.