As to the first, without seeing their internals, they might simply not have enough ad volume from more niche advertisers to cater to such customers. Everyone loves "brand" advertising because the decision to, say, buy a Chevy is essentially unattributable, and they spend a lot on ads to achieve saturation. By contrast, small "product" advertisers might actually expect to see ROI.

They are leaving an enormous amount of money on the table by not inserting their own affiliate links though.