That means your code will stay old.
A new language feature is released, you cannot apply it to old code, since that would make a big PR. You need to do super slowly over time and most old code will never see it.
A better static type checker, that finds some bugs for you, you cannot fix them as your PR would be too big, you instead would need to make a baseline and split it up endlessly.
In theory yes, maybe a bit safer to do it this way, but discouraging developers to make changes is bad IMO.
Obviously depends on your usecase, if you develop software that is critical to people's literal life, then you'll move more carefully.
But I wager 99% of the software the world produces is some commerce software, where the only thing lost is money.
