The pronouns "it" and "they" or "them" are handy but also nonspecific. It's easy to construct a sentence in which it is impossible to determine to what protagonist the pronoun refers. Take the following:

"They bought a red model 6500 and a green model 47NT and it helped them make a profit." Did the model 6500 help? The model 47NT? The act of making the purchase? The sentence seems to make sense, but is not constructed in a way that makes the meaning clear. Someone who has no context could later read your memo, white paper, or other document, and be unable to parse that important information out. Instead, try "They bought a red model 6500 and a green model 47NT, a purchase which helped them make a profit."

"The IT department brought in consultants and, after some disagreement, they decided to terminate the engagement." Who terminated the engagement? The IT department? The consultants? Both sides could have, but I'm sure your legal department would like to know exactly who it was who cut things off. Instead, say "The IT department brough in consultants and, after some disagreement, those consultants decided to terminate the engagement."

Yes, in both cases, we substitute a wordy specification for a short pronoun, but the very substantial gain is in specificity. It's very useful for others to know to exactly what you refer.