Right now they're using QR code menus to push ads and collect/sell your personal data, but the ultimate goal with QR code menus is being able to gather data from your phone (like a device ID), use that to get information about you (like your income level or past purchase history), use that data to algorithmically determine how much money they can extract from you, and then finally push to your screen a menu where the prices are all individualized for you. That way they can charge you more for the same menu item than they changed the person sitting next to you, and you'll never even be aware of it.
Right now the main thing holding them back from doing that is that consumers tend to think this kind of discriminatory pricing is unfair (https://link.springer.com/article/10.1057/s41272-019-00224-3). There's a lot of work going into trying to get people to accept the idea that some people can (or should) get different prices than others for the same goods/services. Prices should be fully transparent and the same for everyone no matter who they are.
Be very careful when using QR codes for anything that results in a displayed price. Maybe compare the prices on your device with what's shown on the devices of the other people you are with, or better yet just insist on paper menus and walk away if they can't accommodate you.