Sadly, I believe this is generally due to human nature. We often go through these profiles either assuming that we are right and know what is best for the profiles, no matter what others might think (which causes these types of scenarios, unfortunately), or:
We presume that we might know something but it could be incorrect, in which case we tend to be a bit more cautious about altering others efforts and also tend to be more communicative and collaborative in trying to discover what is the most appropriate way to make such changes.
I generally prefer #2, which is more in line with the Honor Code, but I also run into the #1 type from time to time. When they make a change that adds to the profile, I tend to ignore it, even if it's a major change. But when it causes conflicts, I try to contact them and ask. If I can prove it's not related to my profile, I even try to be helpful and can even create a new profile for them to put the source and such into to acknowledge that this belongs to someone else. I try to make sure that the "rejected merge" match is there as well, so that in the future someone can see that these profiles were previously conflated. And I'll generally update the biography to indicate that the person was "not" married to so-and-so. But I do try to research it a bit first as I could also be wrong, and I hate getting all flustered only to find out later that they were right.
Just my thoughts.