I don't think evidence exists to suggest they don't. From a burnout perspective alone, making people work in an environment they don't like will cause attrition. Especially now that there are plenty of WFH options. That's not even touching on how stress impacts creativity.
> Qualifying this with "good devs" somewhat begs the question. I would rather avoid judging the developers and just say, no, most developers will not typically write the appropriate amounts of tests by without some friendly reminders.
Our personal experiences are diametrically opposed to each other then. I've never seen lack of tests be an issue on any team I've worked with. I have however seen unproductive teams create tests in place of being productive.