If chametz is batel before Pesach

Question

If chametz can be batel before Pesach, why don't we buy (before Pesach) any commercially produced product with year-round (i.e., not Pesach-specific) kosher certification which does not list chametz ingredients?

Is this just another case of "Jews are very particular with kashrus on Pesach, beyond the letter of the law", or is there something more to it? And if the former then is it binding? — although of course CYLOR for practical halacha.

Update:

Here's an example to work with, for the sake of argument. Suppose a chocolate has the following listed ingredients: sugar, chocolate, milk, cocoa butter, cocoa (processed with alkali [i.e., "dutched"]), milk fat, lactose, soy lecithin (as an emulsifier), PGPR, and artificial flavor.

Answer 1

A few reasons that come to mind:

• The taam of chametz may be absorbed in the utensils used to manufacture that product, and likely there will not be shishim to nullify that taam.

• There may be minuscule amounts of chametz that need not be listed on the label or are included in the generic "natural/artificial flavors", but which are significant due to their potency ("l'taama avida").

• The average layman is not knowledgeable enough to discern which innocuous-sounding ingredients are actually grain based.

This is a question all year round: Why do kashrus agencies go through the trouble of kashering facilities and analyzing ingredients, when they could just rely on bittul and aino ben yomo in many or most cases? The answer (to my knowledge) is as R' Moshe says, that it would be "mechu'ar hadavar" (unseemly) to put a halachic imprimatur on such products. So the same logic presumably applies with regard to pesach.