The reason for this is because standard resumes usually don't include enough information for us to clearly identify films or TV episodes. For example, they rarely mention release years, needed to distinguish between films with similar or identical titles, and they often don't include information on specific episode titles for TV series. Resumes are often very vague when it comes to detailing how a person was actually credited on-screen (several films may be lumped together in a resume under the heading "assistant director" or "camera department" without specifying the proper on-screen credit for each of them).
On the other hand, many resumes often include too much unnecessary/ineligible information (such as stage work or TV commercials) that we can't list and don't need, which hinders and delays our processing. Moreover, unedited resumes will include credits that we already list (often with minor variations on titles or job descriptions), therefore creating duplication and additional confusion.
If you provide detailed information only on missing credits that need to be added or specific corrections on existing ones, we'll be happy to help you or submit the changes on your behalf (assuming we can verify them). However, as explained in our general FAQ, you will need to be extremely precise when you mention titles, names and credits, and most resumes unfortunately aren't.