I can see both sides of this.
There is a website that people post photos on for others to use in any way they want (the registered gallery link). Sometimes if I don't have a photo or can't find a photo from the hybridizer (may be an older one no longer on their site) I will look here for one.
http://www.hybridizer.net/ It does have who took the photo and when I use one from here I credit the photographer.
I do use my photos and I also use the hybridizers photos on the Lily Auction, just depends.
Last year on the lily auction there was this particular HOT selling daylily and every photo was the hybridize'rs photo EXCEPT one, it was the seller's photo. The one that had the seller's photo didn't get bid on (except by me) and it was a double fan while the others were all single fans. So I got a double fan for $50 while the single fans were going for $60 and up. This happened twice so I got 2 DF of the same daylily . And this was a reputable seller so it wasn't that they were unknown or anything. IMHO, I think people scroll through and just look for photos sometimes and don't read the description or search for a particular one and if the photo is not the hybridizer's it gets over looked. I know people want to see what the daylily looks like in others gardens, but what it looks like in my garden can be totally different in someone elses garden. I have good examples of that. It all depends on soil, climate, and what have you. So if someone buys a daylily from me based off my photos, it still may not look like that when they bloom in their garden.
Just my humble opinion
And anyone can use any of my photos if they wish.