Answer:
Because if you are too careless you could make the whole situation even worse, but also risk killing them.
Step-by-step explanation:
If you lose to much blood you could die, basically if you have no clue what you're doing you could cause them to bleed out more or try to help them up and... well you know. Also, you can choke on your vomit, after all that's food coming up not trying to go back down, if that person is vomiting a lot trying to rest them on there back is only probably going to kill them( I'm just saying).