But, since a lot of experienced people & experts seem to do it, I have to ask: WHY?
I have over 120,000 images in my archives. Most cameras recycle filenames every 10,000 images (4-digit counter) which means that if I didn't rename images I'd have multiple files with the exact same name floating around, which can get very confusing. Which 187U5467.tif is the RAW I actually want? So I rename all of my images in the format YYYY-MM-DD_XXXX where Y is year, M is month, D is day, and X is the shot counter for the day. I also shoot jobs with more than 1 camera so that I have an immediately available backup if something breaks, and so I can have a wide lens on one body and a long lens on the other. If I keep the camera clocks synced, then I can sort the files by date/timestamp before renaming and then have all of the shots in chronological order no matter how many cameras I used.
I label the folder containing the images YYYY-MM-DD + a description of the job/shoot, such as "2005-06-23 Grand Canyon North Rim". This lets me find a shoot with a simple directory search. And if a client wants prints of a specific image, all I need is the filename (2005-06-23_1436) and I know exactly where to find it.