A programmatically enforced set of rules is certainly one way to get consistency, but it isn't the only way. You can achieve consistency through culture and training too, and sometimes that's the only way.

Edit: you can look at Google's C-style guide for some examples, https://google.github.io/styleguide/cppguide.html#Structs_vs...

It isn't possible to statically analyze if a class/struct is a POD or if the methods enforce invariants. But it's often very easy to do so with a human eye. And there's value in the distinction!

Similarly, forcing someone to justify using a power-feature (operator overloading, templates, metaclasses, whatever) can only be done by a human. There may be cases where the power feature is warranted and the benefits outweigh the cost, but a linter can't know that. (and ultimately all of this comes back to: things look consistent, and when things are inconsistent, that's a strong signal that something unusual is happening and you should pay close attention)