I have absolutely no argument that the quality of time matters, yet I don't know how you'd go about judging that. I suppose you could give a rating to each flight hour logged. For example, tooling around the sky earns you 0.1 (lowest), and something like flying a multi-engine aircraft cross-country, with inclement weather, and so on would earn you a 1.0 (highest). However, I don't see that ever happening due to the sheer amount of work it'd take, and the enormous mess it'd create. That's why it's simply easier to say "ATP required", modify some of the Practical Test Standards, and completely rewrite the written exams (and keep rewriting them).