The other misunderstanding, much more widespread, concerns whether one should use the passive or not. Many people preach that we should never use the passive. Computer grammar checkers typically flag passives and advise writers to change them. This negative attitude ignores the fact that the passive has a perfectly respectable pedigree in English. It is not hard to understand where the negative attitude toward passive comes from.
Passives are, in fact, harder to read.
Leaving out the agent allows the speaker to avoid assigning blame when somebody does something wrong. But telling writers simply not to use passives robs them of an important tool for making their writing more graceful and coherent. In most writing situations, writers should think of the active voice as the default form, the one they should use unless they have good reason to use the passive. Mike Markel gives four situations in which the passive is to be preferred. In all four situations, the passive provides the desired sentence emphasis.