There are many reasons to cite previous academic work in your papers.
Anything you take from another source (definitions, methods, evidence, etc.) needs to be cited. Even general knowledge, for example, that Joe Biden was elected to be the President of the United States in the fall of 2021, should be cited due to the prevalence of false information widely available.
You need to cite information as soon as you start referring to it. Merely providing the source at the end of a paper leads the reader to question how much of the paragraph is your contribution versus that of another source. Indicate the source early and if the information from the same source continues over multiple sentences, use pronouns, determiners, and linking words wisely to indicate the continued connection. For example, their research also illustrated… they concluded that.
Further information on the appropriate level of citation can be found directly on the APA Website.