I know one C++ library that caches data but never evicts. Instead, the library author expects you to restart your app every 24 hours.
It may not be as simple as "that's our policy". I worked at one place (embedded C++ code, 2018) that simply reset the device every 24h because they never managed to track down all the leaks.
Finding memory leaks in C++ is a non-trivial and time-consuming task. It gets easier if your project doesn't use exceptions, but it's still very difficult.
Was not available for that specific device, but even with Valgrind and similar tools, you are still going to run into weird destructor issues with inheritance.
There are many possible combinations of virtual, non-virtual, base-class, derived-class, constructors and destructors; some of them will indeed cause a memory leak, and are allowed to by the standard.
I love these folklore comments. Post an example.