Hi ya
Think of them as an incubator for plants to give them a good start in life , Seeds have to be germinated in moist conditions and kept warm and moist in early stages till roots form and they can feed from the soil ( or your choice of cloaning aid ) The clear lid allows light to encourage the seed to grow towards what it belives is the sun
, Clones cut from mother plants have no roots and need the warm moist enviroment to promote root growth ... they feed off the moisture in the prop thru the leaves .
Do you need one ?..... depends weather you can create that kind of enviroment without one
.... you can make one from a few things around the home ... as long as it has a clear lid to acces a light sorce and can stay moist for the seed to feed ... Take a look in the DIY section for some good home made Props