Let's say that I have an ancestor with 11 attached sources. It's interesting how many times I have just gone back to review each of the already attached sources, from top down, and found additional information to record from the source. Often other family members that have not yet been added to Family Tree are found. People that are attaching the record hints to FamilySearch, are just not gleaning all the information from the record source they are presented with.
The process of using the FamilySearch "Source Linker" can be a bit confusing at first. It is typical to not know how to use this tool and so some family members may have incomplete sources attached. We can show you how to use this great tool!
Another common problem we see, is that the person attaching the source record, doesn't even look at the actual document. They only look at the index of the document. Always look at the document image to see for yourself what is in it. This is true, for example, with US Census records. There is quite a bit of information that is not indexed, but found in the atual written document. Also, remember that dates or other information can be mis-indexed.
By actually looking at the document image, gleaning all the information from it, and correctly attaching the source, you will be amazed at how much more information will be oome available to you, including additional family members not recorded in Family Tree.