The main downside for the blind guide horse user is having every single person that sees them run up and say some variant of "OMG IS THAT A HORSE!?!?!?!" Even w

The main downside for the blind guide horse user is having every single person that sees them run up and say some variant of "OMG IS THAT A HORSE!?!?!?!" Even with a dog blind persons just trying to go about their business get a ton of unwanted attention and a horse draws an order of magnitude more. One also needs to be able to pasture it. It doesn't take a ton of land, but a guide dog can live in an urban apartment and a horse can't, at least not without being miserable.