So my question is: Why M and Maple do not see right away that int(f'(x),x) = f(x) ? isn't this what FTOC says?
Is it just an issue of parsing? I.e. they will first evaluate f'(x) and then try to integrate the result, and they just need to add extra code to detect that the integrand is a derivative of some function and do the short-circuit FTOC to return that function asthe answer right away?