Amazon is a high volume low margins business. Mass walkouts are very disruptive. Everything stopping 'the machine' translates into direct revenue loss. Amazon went to great lengths in making the machine resilient by having people be more expendable but we're still not at the point in which if a lot of people walk out at the same time, there's an army of scabs in standby to pick up the work and keep things going. If this goes viral and a lot of workers do it at the same time, it can be catastrophic.