As almost anyone who's broken a bone before can attest, hard plaster casts really suck. Seriously, apart from holding a limb in place so that a bone can knit back together, there is no upside to a plaster cast. There's the dreaded taping-of-the-garbage-bag in order to bathe, shower, or watch wistfully from the beach as your friends swim and play in the water without you. There's the strain it puts on the rest of your body, because believe me those things are not light. There's the accidental bumping and scraping of yourself or others because of the cast's solid, chunky, rough construction that could potentially lead to additional broken bones of you and/or your loved ones, because learning to maneuver with something like that on your arm or leg is no easy feat. And then after all of this, of course, there's the crippling terror of having the cast removed, with anxiety over the proximity of the doctor's little buzz-saw to the horrifying stench of withered muscle and its detritus that has not been directly exposed to normal air for six to eight weeks. Additional downsides of the plaster cast could include insulting or just poorly-done drawings and signatures from your friends or family. When your brother decides that it would be hilarious to draw a picture of a penis on your cast, you've really got no other options than to either live with it until your bones heal or attempt to turn it into a rocket ship, which is really not successful because you can barely reach the area of the cast where the original was drawn - certainly not in a way that maximizes your artistic cover-up potential.
Thanks to a guy called Jake Evill, this could all be in the past. While I recommend avoiding breaking any of your bones if at all possible, if you must break a bone, try to wait until this becomes widely recommended and available.