Jest used to be very meh. Also, Jest by default would cater to more "purist" unit testing. Everything mocked, everything isolated, runs in node, no browser.

A lot of people in the frontend world equates unit testing with Selenium tests (aka: integration tests) and get really ruffled/confused by "pure" unit tests.

Now Jest changed the defaults to what most people expect, which will confuse them less, I suppose.