It depends what equipment the vets have, I have had feet, hocks and a horses jaw x-rayed at home recently, mobile machines may be a little less good but when we had the jaw done we had a computer here also so could see the results and take more until we had the angle/ picture we required.
Often they like to have them in to do the full range of nerve blocks and x-rays, running up huge bills that in my view are often not required, nerve blocks can be done at home as long as you have somewhere suitable to trot up and maybe lunge.
Depends on equip, our vets have up to date stuff, did hoof and fetlock at home and could see the xray there and then on the screen was really good, vet could also see where foot needed to be balanced, as farriers don't have xray eyes it was quite handy
Mine did it with their portable machine, but in the vet's car park (I just hacked up), so vet could nip into check the xrays as they were taken, so she knew which extra ones to do, and where exactly to pinpoint. Aparently she couldn't do that if the xrays were taken at my house, so there would have been a risk that further visits would be required to get the right views.
To be fair mutely, renting a machine for the sake of one client( if a small practice) is not an option. Infact, a fully portable digital x ray machine goes for about £40k-45k these days - too expensive for most smaller practices to feasibly equip themselves with. I have one here but it certainly doesn't cover it's costs.
But smaller practices would be more able to get / afford one of those than a full on clinic set up I would think?
OP yes, I have had such X-rays done at yard many times by our relatively small practice.
Ah but there's portable ... And then there's portable! It's the instant pictures that are most expensive and often not justifiable for a practice. There are cheaper non- direct radiograph units( some of which are fully portable and others which must be taken back to the practice).