It's not like these people would walk out if an email would make their point just as well.
Incidentally paid sick leave, which warehouse workers don't have and this protest is in favor of, is estimated to actually save money, not cost it. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5649342/
As best I can tell, there's evidence that everything these workers are advocating for would have no effect on or better for the company long term through people liking the brand more reducing hiring and training costs by increasing worker retention, reducing the lost of productivity associated with sick workers getting other workers sick, etc.
https://medium.com/@amazonemployeesclimatejustice/amazon-sic...
But I guess some people think well paid executives always know better then regular employees.
Personally if I had a say at Amazon, I'd suggest given the 47.3B they had in cash on hand as of nov of last year and how they've been raking it in since people have begun sheltering in place that they at least could afford to experiment.