And then you get another typo in another JS file. So you convert it too. Rinse and repeat. In the end, all your application is now written in typescript, hooray.

Only the number of defects stays the same. Puzzled, you start investigating, and eventually you realize that all of those bugs were shipped by the same person. Turns out your whole TS crusade was a distraction. Even worse: you were optimizing for poor performers at the cost of your best performers.

But when all you have is a hammer, everything looks like a nail.