For the same reason people come out with other stupid suggestions.. they do not know what they think they know.
For example, on another thread currently, a breed known not to be particularly readable, that already has behaviour problems, owners struggling for time - suggestion 'Borrow My Doggy'...
Yes, let's lend that dog who is already struggling, is not easy to read, has behaviour issues - to total strangers who will almost certainly NOT have the skills to help and may well end up making matters worse and putting themselves and their children at risk! Cracking idea!
Greyhounds are great, I love 'em, I've had several both of my own and fosters, but they aren't for everyone.
Some have no prey drive and are tiny, for some people a tall dog that folds up small takes up less space than a shorter, heftier dog that doesn't.
But those are the outliers, most ex racing greys are big, clumsy, have a fair bit of prey drive and need to learn how to be a dog. Not actually what a lot of folk want!