I never thought about their lack of patterns. But then... though they do group their fabrics together, and I guess they call those groups collections, they're not like Moda collections where all the fabrics in a group play well with one another.
To my eyes, the AH fabrics seem to more-or-less stand on their own, individually. With less of a need for a supporting cast.
Maybe that's why they don't do patterns. Or maybe it is because AH's designers are more artists, rather than quilters.
Just a guess...