Why does the Catholic Church make certain demands

Maybe it's because that they are also just people, and that they are given freedom on making decisions on their own. This is the main reason why I don't go to churches, alot of their teachings are way to far off from what the bible has told us to do so. If people and especially those from the church, would just spend their time reading the Bible, then they would realize that most of their doings are wrong. Take for example the images that they put on front of the altar, why would they put it if they know that it is not allowed by God. They already violated a law from the ten commandments..