Electric irons are made of iron, and since iron is a good conductor
of electricity, if you touch it with your bare hands you would get
shocked. Plastic doesn't conduct electricity and is one of the best
insulators, so it would be safe to use plastic handles while
ironing. Even if the ironing machine isn't electric, the machine is
bound to get heated, and if you touch it to use it, you would burn
your hand, so no matter the type of ironing machines, you always
need a plastic handle.