> The compiler support you need in practice is quite limited.

This is true, but it's absent especially in C. Of course, as long as you can intercept writes and/or reads through pointers, you are good to go in principle. However, that solution may not be efficient.

> Cascading deletes are rare in practice

An array of objects (e.g. std::vector<std::string>) already has unbounded deallocation cost. People mostly think of tree-like structures here, but such structures only add the risk of stack blowout to the lack of an upper bound. But in principle, any container that does not have a size limit can give rise to unbounded pause times.