More than likely, because plastic surgeons have NEVER used silicon (essentially purified, melted beach sand). They used silicone (basically a gel) at one time, but that, too, has been discontinued for many years. While they have a common element (Silicon (Si)), they otherwise have nothing in common.
I know this was a (very poor) attempt at humor, it really isn't humerous in any way. It is a very obvious display of ignorance.
Does anybody remember Silicon Graphics (the one time graphics workstation company). I wonder why nobody made jokes about them.