I usually provide sources for all of my posts as I feel that artist recognition is important. That way users can find other work that artist did and so that they can be encouraged to create other work.
Sites like SauceNAO, IQDB, and of course Google-fu are wonderful tools that help people track down sources, so it's a good idea to bookmark these.
SauceNAO has an official extension for Chrome and Firefox that expedites the process, and includes IQDB, Google and TinEye. Right-click the image; easy search in no time flat.
If you have time to rehost the picture on Imgur and post it on Reddit, you definitely have time to use a simple browser extension, right? (Time constraints is frankly a pretty poor excuse as is.)
It's just a courtesy, yes, but an appreciated one, and one that's become customary on popular subs like /r/awwnime, as it helps people find new artists to follow.
Additionally, sometimes the source will have a higher quality version of the image, depending on the methods used to find it in the first place.
That's really cool! If you have a product name for it I might have to add one to my collection. I never really thought much about art books until someone gifted me Fate/Complte Material.. One of the best gifts I've received seeing as I haven't played the visual novel and it covered all routes + official artwork.