I agree somewhat with you, but might be able to put a bit more perspective on this.
Photographers use their work product as advertising, so attach their name to their work. They also often do any retouching themselves. This, along with copyright preventing modification of the images, allows those images to accurately reflect the abilities of the photographer.
It's a lot like software licensing in that way. As a company, you don't necessarily want someone tweaking your software you've sold to the and either expecting support, or even just possibly leaving a bad association with your software for the people that use it that don't realize that the reason it may be unstable is because someone has made unstable changes.
That doesn't make it good, but it does explain their thinking somewhat. Photographers are like software consultants, but because of the different time they came to prominence, they've managed to make it the norm that they retain rights to their work product. This is changing though. It's not too hard to find photographers that are willing to just dump the images to DVD pre-retouching and hand them over for you to do with as you wish. It won't be cheap, because they are losing out on being able to upsell you albums and video collages, etc, and their cost reflects not just the time they spent there, but their experience in knowing where to be and what to do to get the best pictures (in the same way that someone that pays my consulting rate is paying for my decades of experience).