This blog cites a load of reasons given by style guides. The conclusion is basically that contractions can carry an informal or friendly tone - which you may or may not want in your professional writing, depending on the professional context. Some guides also say that contractions can make writing harder to read for non-native English speakers (well, readers).
The Associated Press Stylebook: "Contractions reflect informal speech
and writing. . . . Avoid excessive use of contractions."
Microsoft Manual of Style for Technical Publications: "Avoid
contractions. As basic as contractions are to the native reader, they
add unnecessary complexity for the non-native reader. For example,
contractions that end in 's can be mistaken for possessive nouns, and
the 's can be read as either has or is."
Personally I use contractions all the time in my writing at work (emails, internal reports and documentation), but I might avoid it if I were writing reports that were to be shown to clients or investors, or if I had a more formal or uptight boss.