Here is a possible scenario:
If you have a 3rd great-grandfather for instance with two profiles that need to be merged--some of your cousins' DNA information might show up on one profile and your own family might show up on the other. The two halves are not connecting and will not connect until merged.
The way autosomal DNA information works on WikiTree is it will filter up your tree to all of your profiles to eight degrees of separation. BUT ONLY TO THE PROFILES CONNECTED TO YOU!
Here is a question I have been asked: If my DNA information does not show on a profile that looks like it matches one of my profiles are they truly a match? Yes! Your DNA information will not show up on the profile needing to be merged with yours because it is not yet connected to you.
This is just one more reason why merges are a very important part of keeping our tree healthy and helping it meet its full potential.
You can search for potential merges on your tree by going to:your Watchlist and clicking the "Find Matches" button at the top.