dragsters of the 60's didn't need them. Single hoop cages allow you to exit easier without having to stand upright in front of the axle. With double hoop, you you need to lean a lot further forward to get your butt clear of the cage to stand upright, hence the wheel ends up between your knees.
My cars a bitch to get in and out off but its got the look I wanted so I'll have to suffer. Cant be any worse than my 23T altered, a cockpit opening 3ft in the air with nothing to stand on, guess thats why flip up topolinos are so popular.