Why is it so often that someone has gone to the trouble of "verifying" the cast and crew as complete, when it so clearly is incomplete?

I go to a title page, and seeing missing cast and crew members, I go to add them, watching the credits carefully, from whatever TV show or movie I am watching, and I add what is missing, sometimes just one or two, and other times ten or twenty or more.  When it is a large number, it is usually in one of five categories, cast, thanks, transportation, stunts, and/or miscellaneous/other.  Only to receive a warning that I am adding to an already complete cast, which I override, since I am sure the credits are incomplete.  Just yesterday I added a bunch of missing credits in cast and thanks.  The thanks were allowed, but the cast members, all listed extras, were DENIED, due to being unable to verify.  I am very curious, how did IMDb staff go about verifying (or being unable to verify) what I submitted?  I promise that I submitted valid cast members, specifically listed in the credits as "Party Extras."  It would seem that because the firsts submitter of the title was too lazy to submit the extras listed on screen, that IMDb.com staff took that submission as FACT, when in fact (no put intended) it was not fact, but fiction!  So, just how does IMDb.com staff go about verifying such things, or are they too lazy also?  I have come to believe that when a whole large group of new credits are submitted to one of those vaunted "cast and/or crew verified as complete," they just lazily wait two days, and then send an automated "DENIED - unable to verify."  This has happened to me dozens of times, enough times to have denied me top contributor status at least twice.  But, more bothersome and troubling is, I have made an effort, I have done the work, only to have it discarded like so much trash.  How can this serious problem be rectified, and why does IMDb.com wish to continue with incorrect records, when someone has taken the time and made the effort to correct and complete those records?  By my experience AT LEAST 50% of the titles with "cast and crew verified to be complete" are actually INCOMPLETE, sometimes excessively so.  Why is this allowed to continue, and why even have the "verified to be complete" as a feature.  It is kind of like continuing with the death penalty, every year, there are people who are NOT GUILTY put to death, just because someone has been lazy, or the first person, who accused the person of guilt, is to be believed over and above every other person who submits evidence to the contrary, who are thence not to be believed, in most cases, just because they came along second?