If you were starting a new project you could put lints in place to make these things enforced. But at some point you have all these lints and customizations in place, and you can't use old or 3rd party C++ code any more because of them, so you begin to ask, why not just use a new language where this stuff isn't pasted together with glue and bailing wire?
My point is really not about the code you write yourself, but the code you need to include in your project. Rare is the professional programmer that always gets to finish their project using only code they wrote themselves, and for many projects that's highly inadvisable (don't roll your own crypt unless you have a very good reason).
So, given that at times we will have to use external libraries, and given that even very safe languages often have escape hatches meaning you can't be sure the code of one language has more constraints than another, it would be great to have other indicators than the language it was written in that indicated what safety checks it uses.
If next year you're writing a new program in a language that hasn't even been invented as of now, and is viewed as safer than every language out today, what does that actually get you if one of your constraints is that you need to include and use openssl or one of a few forks for compatibility reasons? Wouldn't you rather be able to look at the available options and see that come opt into specific safety constraints, and have been good about not them circumventing them, and do so extremely easily? Network effects and existing known projects seem to have an inordinate amount of staying power, so we might as well deal with that as a fact.
The world is a messy place, but the more information we have the better our chances of making order out of it, even if temporarily.
