Ok whatever it is, the price on display is not the final price, and I feel scammed.

They're not different to the consumer. Either way they're a surcharge to the store price of the item, and most places in the world include it on the sticker.

I don't see how the system would change unless people stop tipping, but as a foreigner I don't see it as my responsibility to change their system.

The simple rule of thumb is: if you are in a full service sit down restaurant (waiter takes order and then brings you your food, tipping is expected, and not doing so is seen as a major dick move, because it directly stiffs the waitstaff. The only time you should not tip in this situation is if the service is absolutely horrible.

Any other situation, like ordering at a counter and then going to get your food, or any fast food, tipping may be offered as an ask on the kiosk, but it’s never expected (not in my opinion deserved.).

But simply: if you are waited on, too 20% and be done with it.

And that'll only hurt the poor employee's efforts to pay rent this month. The employer could care less, and sure you may make them mad enough that you're the last straw and they quit, but I'd be hard pressed to think you're magnanimous for it.