One of the reasons photographers do not deliver unedited photos is that they could be compared to negatives, the photographer have full rights over them. Even when a photographer is commissioned, the clients always pay for the final product.
2. Brand Value
You've spent some time choosing the right photographer for your project. You chose your photographer because you like the style, the angles, the felling that the photos convey.
That's what makes the photographer's brand. And so, delivering unedited images would be damaging to the photographers brand as there is no guarantee those image will never see the light of day. This could strongly hamper the photographer's reputation.
3. Files size and accessibility
Raw files are HUUUGE. They would use an insane amount of storage space.
Raw files also can't be opened with a regular app or program. You would need an editing software to be able to open them. The photos need to be processed into jpgs to be accessed easily.
4. They just don't look good
Honestly, they don't even look good. They are like a canvas without paint on it.
That's a shame to hire a professional photographer to end up with amateur looking photos.
If there are some adjustments needed on some of your edited photos, more often your photographer will prefer to re-deliver adjusted images rather than give the unedited photos.
5. How to make sure you end up happy with your photos
Choose a photographer with a style of photos that you truly like. Don't pick the fist photographer to come, analyze portfolios and communicate your expectations for your final photos with your photographer.