dumb question, but why would it not be a good idea to enclose the blades so anyone walking up to it won't be hurt? (just a simply loop / bumper arrangement? on

dumb question, but why would it not be a good idea to enclose the blades so anyone walking up to it won't be hurt? (just a simply loop / bumper arrangement? on a side note, I hope to be around where a Blade Runner like Spinner is a thing or at least a possibility