Also, user comments in the Reddit thread about the "comfort break" incident indicate that AWS is Amazon's primary source of revenue these days. This is backed up by much of Amazon's own PR reporting. For a boycott to have any meaningful impact against Amazon, it would have to include a hit against that revenue.
Call it pessimism, but it's my opinion that few if any companies will incur the costs to move their own business out of Amazon simply to penalize them for poor working conditions in another section of the company.