You're not flying to Hawaii for free. Every single purchase you made with the card was more expensive than it had to be, because the merchants needed to cover their credit card fees.

What you're doing is the equivalent of always paying with bills, and dropping your spare change in a jar. And when the jar is full, you buy a ticket to Hawaii with the money in it. Except with a credit card, they keep the jar, take half the quarters, give you back the rest, and make you feel grateful for the entire experience.