Agents write and review most of it now, and they catch a lot. What they cannot do is open your product and feel that something is off. A person can, in about a minute, and that minute costs less than the tokens you burn asking a model to guess.
You ship a change that touches a shared component.
It reads the diff, decides the blast radius looks small, and never opens the one screen where that component is now broken. You pay for a long run that concludes everything is fine.
They click through the flow, see it, and tell you which screen. Under a minute.
You ship all week and never open the site on a phone.
Every assertion passes, because the layout is technically rendering. Nothing in the run tells you the button sits under the keyboard on a real handset.
They pick up a phone and the problem is obvious in the first screenshot.
$200/month