where I work, we're not allowed to merge them. we test every change, and we review everything to make sure there are no regressions in all the obvious features. scrolling through our webpage will never break in production, because we use people with a full set of eyes to check before merge.
I believe you but I've literally not worked at a single place that puts that much scrutiny on PRs and I've been working as a professional programmer for 20 years.
