Olivia Chen of Cowen & Co. recently outlined why she believes Amazon should buy Macy's. Her reasoning consisted of a few reasons:

Tremendous vendor/supplier scale: Macy's would give Amazon access to a whole bunch of new apparel brands and help expand its first-party seller relationship.
Speed: Amazon could take advantage of Macy's vast number of physical stores and warehouses to improve delivery speed.
Big data meets retail: Amazon has the "best" predictive analytics technology in retail, so it could help Macy's make better decisions across inventory and pricing, and potentially lead to higher sales.
Merging physical and digital retail: Amazon would gain foot traffic from loyal department store shoppers and get to utilize Macy's physical presence to showcase products and have customers return products easily.

None of what she says is wrong but the idea of Amazon buying the largest department store chain doesn't make a whole lot of sense. Amazon isn't interested in the high legacy costs burdening the old guards of retail leading to their downfall. Amazon isn't interested in stores that are 150,000 to 250,000 square feet in prime real estate locations. Amazon has historically bought businesses with similar models to their internet pure play mentality. Examples being Quidsi/Diapers.com, Zappos, Shopbop. Macy's is none of those and requires extensive cost cutting and store closures to ready itself for the type of business consumers are demanding.

Bottom Line: Amazon isn't willing to pay for the price of history and would prefer to continue building a leaner business with marketplaces and small format stores. Whose to say that Macy's won't be half the cost it is now in 2-3 years?