Richard Smith, quoted in the document I linked as saying "I do not have any confidence this optimization would ever become reliable in the way that, say, certain forms of NRVO are," is the code owner of the clang frontend.
Heck just using std::numeric_limits<int>::min() will incur a function call in -O0, but nobody cares since it gets optimized in -O1 and up. The same thing applies more and more as you invoke templates from templates, but, again, nobody cares since we are confident it'll get optimized/inlined easily.
It's not nearly as prevalent in modern code since constexpr static variables are now a thing, but relying on these optimizations has historically been super important.
You can choose to use classes and inheritance without using virtual calls, which means that you won't have to use vtables at all, compiler or not. You can rely on the compiler to optimize return values but you can also use a return parameter and not rely on that at all.
I'm not saying that it's a bad thing to do it any other way but I maintain that saying "just make things easy and let the compiler sort it out" is very much not how C++ has been designed so far, for better or worse.