A: They have been around longer (when generally talking to a child) meaning they think they have more experience.
B: Usually they are the soul breadwinners in the house paying for all the kids taxes and bills etc, it may vary from house to house.
C: Since they like made you, for lack of better words, they feel they have authority and superiority over their creation i.e children.
So yeah, parents can sometimes act like dictators but generally are only looking out for the wellfare of their children, I know this doesn't apply to everyone to whom I give my condolences but I'm only stating the stereotypes. (editing to this is appreciated).
"See, to them, you're just a freak... like me!"
"Let's put a smile on that face!"
"Heads you live, tails, you die"
"This party is pointless" "Everything's pointless, wanna go talk about it?
"Everything you care about you destroy"
"3 Words, Disgruntled Radioactive Clone"