Funny isn't it, what you think about. I loved my trike as a kid. proper bike, proper brake, rod type. Went funny on the bends and only frove one wheel, so I could go round right hand bends quicker than left handers, because the wheel always left the pavement.
It was welded several times, and i was distraught without it.
I could never ride a recumbant trike on the road. No, Nay, Never! I won't be a wild rover on one o' those abominations! And what flag would I fly? Jolly Roger? Looks like a chainsaw coming towards you. And a front end collision requires a fender to make it safe, and look nicer for peds.
I have however, seen many 2 wheeled versions. With flags, with mirrors, with things that stick out to deter cars from getting too close. Brave guys!