I recently moved a site for someone from their hosting to my own and noticed that the uploads folder was over 50 meg!
It only had 30 or so photos in it but all of them had been uploaded at the same size as they came off their camera. It works as she only has one site and I am not worried about the space she uses, but what if you have 10 or 20 sites all like that.
Pretty soon your hosting is full of huge images that don’t need to be that way. It is a waste of hosting space, a waste of processing power and generally not a good use of resources. Resizing images is easy to do and you can use an online website for free.
A lot of the free places to work with images have closed down. So I am now using Gimp - http://www.gimp.org/ - simple to use and free
Resizing your images may seem like a small thing but it really is something that can help. Renaming your images to something more search engine friendly is one of the best benefits.
Hope it helps