If your co-workers are also proof reading their own work, and having similar issues proofreading what they are too familiar with, then your time and theirs will be more effeciently utilized by proofreading each other's work. So they find mistakes you could have corrected, and you find mistakes they could have corrected, but all these corrections get done with less time and effort.
Some more background: We're a small enterprise (boss, six employees, secretary, two trainees). Except our secretary and the trainees, everybody has an academic degree. We did try to institute that as a rule, but only me and one person working from home office consistently do so. The person working from home office is also, at the moment, very busy because of some deadlines, so I can't ask him to proofread. The others do proofread, but don't ask for proofreading in return, which makes asking low-status. They are either better at proofreading than I am or ...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.