Human beings are checking those tickets, and movement is proof of liveness (and not a screenshot you and 25 friends are sharing). Many ticket checking systems are not connected to the internet and cannot/will not check if it's already been used. Many of the motion enabled codes are also basically working in the same way as 2FA codes: your ticket is given with a public key, usually unique to your device, and rotates every minute. Allows them to ensure that the ticket is up to date, not forged and signed properly.