You're Carrying Trillions of Life Forms That Also Have to Be Transported
Of all the different types of teleportation that have been thought up in science fiction, they basically all involve disintegrating a human body, shooting it to another location as some kind of data signal and reintegrating it on the other side.
So that would imply that The Fly was onto something when it warned against stepping into a teleporter while something else is in there with you. Jeff Goldblum wound up in the pod with a single fly, but that was enough to confuse the machine, because it was only expecting Goldblum. Having to deal with two life forms instead of one, the system combined them, creating the horrifying human/fly monster.
Life finds a way.
But The Fly was playing it pretty conservative. If Goldblum tried out his machine in the real world, he would find his transporter trying to separate him not just from the fly, but from around 90 trillion other organisms. That's right, trillion. We don't even know how much that is.
Blauerauerhahn, Wikipedia Commons
These little guys have some prime real estate on your eyebrows.
That's because no matter how often you shower, your body is host to a ridiculous number of foreign organisms, from fungus that lives on your toes to viruses that live dormant in your system to mites that live on your eyelashes to the 300-cell-thick coat of bacteria on your teeth. And if you're thinking that all you need to do is develop some kind of better decontamination procedure, think again -- a lot of those microorganisms are your friends. You have bacteria in your gut that helps digest your meals. If you're a lady, your vagina is packed with little elves called vaginal flora that help protect you against yeast infections and other ladyborne diseases. All of that shit needs to make the teleporter trip with you, if you don't want to be extremely sick when you come out the other end.
Somehow, we expected vaginal flora to look more ... Smurfy.