With the very limited B1 exceptions you cannot work in the US on a B.
Do people take calls, answer emails, well obviously, there are probably a lot of minot things people do that could be classified as work, can I mow the lawn to help out whilst I am here? And of course millions just work illegally.
I know some countries, Canada for example have no issue, others have a specific visa for Digital Nomads. US does not.