I couldn't agree more. I've worked at places where some of the engineers were conscientious about writing tests and having excellent test coverage. Guess what? Our services were still unreliable because the engineers who didn't write tests brought poor quality into the codebase, so we had constant problems.

Even a few engineers on the team who don't write tests can make the product as unreliable, from the customer's point of view, as it would be if none of the engineers wrote tests.

At my current company, test coverage is taken seriously as a job requirement, and it is considered during performance reviews. Consequently, the test coverage is pretty darn good.