That is the topic of my latest Bloomberg column, here is one bit about why they might not:
In any of these Washington area locations, Amazon is taking an implicit stance on the nature of talent and education. It’s well known that the D.C. area has high education levels, including in science and technology fields. At the same time, it has not bred a lot of rapidly scaling, dynamic startups comparable to, say, Silicon Valley or Austin, Texas. The work ethic and competition here are strong, but the orientation is too much toward the government as customer and arbiter. If Amazon settles in or near Washington, the company is betting that educated human beings are flexible and can reorient their priorities and ethos to a changing business environment. If there is any argument against Amazon picking the D.C. area, it’s this one.
There are many more points at the link.