It is because much Catholic doctrine is logically based. That's not meant to say that Protestant doctrine is by contrast illogical. What I mean is that,the Protestant often will say "Show me this in the Bible", where he wants to see a certain doctrine quite literally laid out on the page, such as "Jesus is God". Conversely, the Catholic Church will tend to logically deduce things from various bits of Scripture. This is where many of our "unique" doctrines such as Mary being ever-virgin and sinless, works vs. faith, the papacy, and purgatory come from. Also, we have Tradition to refer to which deals with things not specifically dealt with in the Bible.
Most of which was just "made up" in medieval times (such as the selling of indulgences) which is why we split off to begin with. We wanted to get rid of some of that excess non-Christian baggage. Why did you split from the Eastern Orthodox?
Actually, protestants like to see what scripture teaches clearly. There are, of course, doctrines like the deity of Christ where there is not an overt statement, but many passages that teach it.
Stuff like the holy water and Mary remaining a virgin or being sinless, well that seems to be a belief in search of proof.
Anyway, I appreciate your response. AMPU