They come here because none of those have worked - they may be successful for other horses, but they haven't worked on these horses.
Occasionally, in a last-ditch attempt to keep the horse in some form of gainful employment, the vet has suggested that the horse be worked on bute.
There is a logic to this, if you view navicular or DDFT or collateral ligament damage as a degenerative condition that will get progressively worse no matter what - in that case, working a horse on bute allows it to carry on a bit longer and since the inevitable deterioration is unavoidable, there is no real downside.
The problem though is that the pattern of improvement we see here suggests that its more like a repetitive strain injury - so if a horse is landing toe first or has a medio-lateral imbalance, then the longer that goes on the greater the damage will be. Once a horse is landing heel first on a balanced foot the strain is reduced and over time damage can start to repair.
In this scenario, working a horse on bute can actually increase the damage - allowing a toe-first, imbalanced landing to continue without the guarding effect of pain will result in greater strain and greater damage.
Its certainly the case that the horses which come here having been worked on bute take considerably longer to recover than those where the owners have refused to work a horse that "isn't right". Working these sorts of horse on bute isn't the end of the world, but its something that should be very carefully weighed up, particularly when the horse has compromised biomechanics.