When I was running a trainer’s barn, we STRONGLY recommended are chosen practitioners (vets, farrier, dentist, etc), and had very good reasons for both why we chose the people we did (best of the best) and why we liked all our clients to use them (everyone on the same page, similar treatments for similar issues, staying in the loop with horses’ in training, etc). We made using our people more appealing by not charging to hold and doing the scheduling for the clients (clients were billed directly and always knew when the vet or whoever would be seeing their horse so they could be there if they wanted). We never said no to other vets, etc (with the exception of one certain vet who was a complete ass and bad at his job), but would charge or have the owner to the waiting around.
Gotta say, that worked well but our people were VERY good. The few times a client would come in and be determined to use their own person, they often quickly changed their minds when they saw the quality of our practitioners.
I NEVER saw a kick back, except for occasionally a few dollars off a dentist bill or something. But that was more because I would spend hours assisting them. It was more a thank you for my help than a kick back of any sort. The biggest benefit I got was some vets were a little lenient with how quickly I got my bill paid, knowing I worked for chump change.
I have also run barns where it was a free for all, and it sucked. I never knew who was coming and going, certain boarders seemed to have a herd of vets constantly dealing with their horses and their “treatments” were constantly changing. To top it off, because of my employer’s policies (and they didn’t work in the barn) we didn’t charge to bring in and hold for the dozens of different people in and out. So, I spent a good deal of my days schlepping horses in and out.
That was basically a lot of story to say forcing you to use their vet is bad. But a lot of trainers like to have consistency in their programs which is why there may be a chosen vet in the barn. Recommending and forcing are two different things.