Annotated bibliographies are important steps during the research process. As you move further along in academia, the breadth of your research may increase, meaning the number of sources to consult may grow too large to become easily manageable. Having an annotated bibliography is a practical way to keep track of all your sources, as well as encourage you to read through each one more critically than you would if you were simply just collecting information.
When it comes to the idea of scholarship as a conversation, creating annotated bibliographies is a great way to contextualize how your own research and voice fits within what has already been said about your particular topic. Additionally, some annotated bibliographies are published, and in doing so they provide a comprehensive and concise look at the current knowledge of a topic. Looking at other researchers' annotated bibliographies may even influence your own.