At the barn I feed and work at several owners know nothing about what their horses eat, the supplements they get, etc. My BO just tells them what they need to buy and they buy it. I discovered this when I was asking an owner about her horses' food and she told me she didnt know anything about that, we did it. That's happened with another onwer also...lol.
Many people who board have no clue what their horses eat, how much, or even what supplements their animal is receiving.
I always wanted to know what was happening with my horse, but some people don't care or are too confused about how to go about asking.
Instead of making fun of folks like that, maybe offer a class or training session? I think an exam prior to that would be a good idea, since that will tell you their strengths and weaknesses.
I know when I brought my boys home for the first time I wasn't exactly scared, but I was fairly clueless about how much I was supposed to feed them. Oh, I knew WHAT they were eating, but the amounts were kind of sketchy in my mind.
I've had horses for 32 years. For 27 of those years I boarded. It's completely different when you have them at home, and it can be a trial by fire. Sure, you can be as prepared as humanly possible, but there's still a quantity of unknown.
After all, what people who work with horses as their job see as just regular knowledge that anyone should know, isn't necessarily true when it comes to those who board their horses and leave the responsibilities of day to day care up to someone else.