Our paying customers don't appreciate bugs. A layer of testing _is_ fail fast/early because it prevents an issue before it gets to the customer.

One gig I had: several times per week the site would go down and nobody could log in. People were just pushing code and yolo'ing into prod. Paying customers were churning. The solution? A single cypress test on a canary node that logged in and edited one setting. 2 or 3 minutes of barrier to production and now the site doesn't go down periodically with deploys.