General Kashrut Question

Question

I don't understand why you feel the hekhsherim are not helping when it comes to kelim. Granted, if we don't know if a product has been produced on the same equipment as non-kosher products in the same day, then it is kosher, but why isn't a good thing to take away the doubt? Isn't the Shulhan Arukh just giving you an ex post facto (be-dieved) situation, that if you don't know you can eat it, but if you can determine for sure, shouldn't this be better? After all, if you were told that the Kraft marshmallows were made on the same line as a non-kosher product, there is a pretty good chance that both could be made in the same day. Why not avoid the danger and GUARANTEE that the kosher products will not be made with the treif stuff? This would seem to be the lekhathilah approach. Since there are so many products under kosher supervision, why should we rely on the be-dieved (if I am correct that it is indeed a be-dieved)?