Tickets can and do sell out. If you wait until you arrive at the gate, you risk the park being at capacity, making your travel costs a wasted expense.
Buying online allows you to skip the long ticket booth queues, which can save you an hour or more of prime park time. How to Actually Save Money Online cheaper to buy disneyland tickets online
While the base price at the gate is identical to the official website, online platforms offer several ways to secure a legitimate discount: Tickets can and do sell out
Disney uses biometric finger scans or photos at the gate; if someone else has already used a day on a multi-day pass, it will not work for you. How to Actually Save Money Online While the
Scammers may sell a ticket, report it "lost" to Disney to get a replacement, and leave you with a deactivated barcode.