Posting pictures to Wikipedia

Here we have a completely innocuous image, uploaded by User:Mattes, that shows a flight attendant's demonstration of an oxygen mask. It used to be on the Pre-flight safety demonstration article.

My question is: are a majority of Wikipedia pictures taken by users for the intention of getting on the site, or uploaded later because a user realized he had one that could illustrate an article? In this example, did User:Mattes take a flight and just happen to snap a photo of the demonstration, or did he take the picture with the intention of uploading it?