I do offer RAW files for my photos but I don't give them automatically purely because of the size and difficulty to use. A RAW file is substantially larger than even a max quality finished JPEG. Additionally, a RAW file is of no use without a photographer to develop it. It is just raw sensor data and still needs things like color grading and exposure controls and possibly cropping before it is a good photo.

Personally, I offer to give copies of any RAWs the customer wants, but I also preface that with an explanation that the RAW files don't represent final works and are only useful if they are going to touch it up or have someone touch it up.

Many photographers don't like releasing that much control of their images. They may be willing to release a full quality finished product even if that gets mangled, they know it started from a good place. RAW files on the other hand could be associated back to them as a negative thing since they are not finished products and may be poorly handled.

Then there is the photographers who simply want to be able to charge for every use of an image and thus only provide limited quality images to start with so that you have to go back to them if you want larger prints. Personally, I despise that practice, but it is still very common.