Many people find calculus hard to understand. This is especially true of people who have never been taught calculus. Who could expect to understand a complex subject without having first been taught it? No one who doesn't understand calculus would reject it as false just because they don't understand it.
Another complex subject is the relationship between grace and the sacraments. Many Protestants do not understand how the idea of salvation by grace alone and the sacraments fit together because no one has ever taught them. Yet, oddly, many of these people DO reject the sacraments as false, even though they have almost no understanding of them whatsoever.
Given that the very students of the apostles believed in the sacraments, and the sacraments have a two-thousand year history in Christianity, wouldn't it make more sense to study the sacraments to clear up any confusion rather than simply reject them out of hand?