Purpose of limit orders?

This is more of a question. I'd figure I'd ask. Whats the point in a limit order when buying shares if the price you type will be bypassed and you will be forced to by at a higher stock price? Ex: I buy a shares of company A. I put a limit order for $84.50. The price is hovering over 85.50 and rising. Order partially fills due to dip. Instead of the order buying at the limit order price, it buy partial share at that price and buys the rest of wanted shares at $88.12 per share. For this example, what is the point in the user typing the number 84.50 if its gonna force buy at an insane $88.12 a share that didn't even show up on the graph. This may be a stupid question and I'm here for the hate. Thank you for your time.