You can store up to 900 trillion dollars with 0.01 cent resolution in an int64. I doubt many applications need more range than that.

> when [integers] overflow, they usually “wrap around” silently

If you want to write an application handling money, you really want to use a Money type of some description, regardless of whether the underlying storage format is an integer. So it's very easy to avoid silent overflows, since basically all languages that are prone to them also offer primitives that check perform addition, subtraction and multiplication with checks for over/under flow.

> The implicit decimal point is hard to change and extremely inflexible

If you have a Money type, it's not hard to change. The pain point would normally be serialization, but that's not necessarily different from using decimal floating point internally, since very few APIs, serialization protocols or even databases have native support for fp decimals either.

> The number of subunits in currencies change with time in the world.

I suspect Goverments are equally or more likely to drop trailing zeros (e.g. Iraq did not so long ago), which you also need to deal with anyway and which does not get easier by using a floating point format.