You are ignorant.
Have you ever heard of a thing called a heart attack? Well, there's this organ called a heart and it is a very strong muscle that is important to humans. For it to function blood vessels help deliver oxygen to the heart muscles via blood vessels called arteries and arterioles etc. that are embedded in the heart, so it can continue to work. Well, sometimes one or more of these blood vessels gets blocked which means that the muscles get no oxygen and soon after the muscle dies. That is a heart attack.
All muscles need oxygen to live and function. If there were no blood vessels in the muscle every single muscle would die within minutes because they'd receive no oxygen, like in the example above. Hence, it is very possible that a bubble of air from a syringe could be injected into an intramuscular blood vessel and spread to other parts of the circulatory system and result in an embolism. That is why it is protocol to always make sure that there is no air in the syringe. Do you think that they do it for shits and giggles or that they don't know what they're doing and you know better?
Laugh all you want (you actually had no real, intelligent or factual reply other than an emoji) because not only is the joke on you but you ARE the joke. And an ignorant one at that.