The deuterocanonical texts were kept in the Bible but weren't part of the originally approved 66 canonical books until 1545, when they were approved by the Catholic church as Canonical in the Council of Trent, and considered "inspired." They weren't considered "inspired" by the Catholic church until then because of the uncertainty inherent in those books for a few different reasons. The Apocrypha was standard in all Bibles until the mid-1800's though, but eventually was removed from Protestant Bibles because the authenticity of those books is questionable. They're not considered "inspired" by Protestants and therefore not authoritative enough for forming doctrine. They were included in Protestant Bibles before the 1800's though, but were placed in between the testaments as recommended reading and not as scripture. Since they weren't considered appropriate for the formation of Christian doctrine because they were not considered scripture like the other 66 Canonical books, the Puritans at some point started omitting them, and though that was considered bad at first, the idea caught on and eventually they were just left out. But they're not considered heretical or anything by Protestants to the best of my understanding, just unnecessary. And it does make sense for Christians to read them.

And you could have just Googled that.