We are usually told to cite our sources because it allows us to go back and find things again if necessary and it assists us in the analysis of information.
Another reason: Reducing errors created by the researcher.
Creating citations after the research has been done can be time consuming, tedious, and repetitive process. For that reason, it's a good idea to capture information needed for the citation as the research is being done.
That's especially true when creating digital images from microfilm at the Family History Library in Salt Lake.
The screen shot shown in this post shows the file name I used for an image taken from the section of deaths in the records of the Evangelical church in Aurich, Ostfriesland, Germany. The entries are unpaginated and they are organized by year. My goal with the file names is that they be long enough to contain relevant detail to get me back to that image if I needed to and to allow me to find the file by searching on the contents of the file name--just in case I save the file and can't remember where I saved it on my computer.
When taking digital images of the desired record, I always make an image that includes the record of interest and the "top of the page" (usually the whole page to be honest). There are several reasons for this:
- sometimes the top of the page contains headers--particularly in those years when records were written on forms
- it's easier to analyze handwriting when one has more than one entry from the register
- interpreting the item in context can't be done if there are no other entries to provide context
- the top of the page frequently contains page numbers
- the top of the page often contains other identifying information
Sometimes page numbers are on the bottom--that's when copying the whole page is advised.
Then I usually copy just the item of interest, magnifying the image to make it easier later to read all the image.
Turns out there's another reason I should include the entire page: reduce the chance I make careless mistakes.
The file name I used to save this image included 1838 for the year of the record.
The year listed on the actual record is 1839.
I was simply off by a year.
If I had only made an image of the entry for Ameling, the year would not have been included--just the month and day.
And then later I would have wondered why I was off on his death by one year.
And someone else could have copied that information and it could have been repeated over and over.
But...because I made an image of the entire page, I caught my error.
And I caught it because I was thinking about citations while I was actually researching.
One more reason to cite your sources.
The recent update on FamilySearch of the 1892 New York state census reminded me that the name of one family for which I was looking is always hopelessly misspelled: Desmarais.
But let's be honest it slows down the data acquisition process. Researchers get excited about locating information. They rarely get as excited about capturing the raw data from which to craft a citation.
Circuit court case files generally contain court findings, reports, depositions, statements, subpoenas, motions, etc. 
If one only looks at the database entries in the "Evangelical Lutheran Church of America, Records, 1875-1940" at Ancestry.com it's possible to draw some off-the-wall conclusions. That's true though with any index--not just those at Ancestry.com. Researchers who only look at index entries potentially create bigger problems than the actual records themselves. A look at the actual record may clear up what appears unusual when only looking at an index or database entry. 
This database is showing as new or updated on FamilySearch since our last update:
Indexes are finding aids to be used in conjunction with the records they index.
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